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Saturday 31 December 2011


Kinematics Terms
Terms
Kinematics  -  Kinematics is concerned with describing the way in which objects move.
Displacement  -  An objects total change in position. If a man runs around an oval 400 meter track, stopping at the precise location he began, though he ran a distance of 400 meters, his total displacement was 0.
Dynamics  -  Dynamics focuses on understanding why objects move the way they do.
Reference frame  -  The coordinate system with respect to which motion is being described.
Speed  -  A measure of how fast an object is moving.
Average velocity  -  The time-average of the velocity function over a specified time-interval. (See formula below.)
Instantaneous velocity  -  The value of the velocity function at a particular instant in time. (See formula below.)
Gravitational acceleration  -  The graviational acceleration of objects near the earth's surface is the same for all objects regardless of mass and is given by the number g = 9.8m/s2 .
Scalar-valued function  -  A function that outputs scalars (regular numbers). Most common functions that you are probably familiar with are scalar-valued functions.
Vector-valued function  -  A function that outputs vectors. This means that while the domain of the function may consist of scalars, the values in the range are all vectors.
Position function  -  A position function can be either scalar-valued (for motion in one dimension) or vector-valued (for motion in two or three dimensions). At each point in time its value represents the position of an object at that time.
Velocity function  -  This function is the time-derivative of the position function, and gives the velocity of an object at each point in time.
Acceleration function  -  This function is the time-derivative of the velocity function, and the second time-derivative of the position function. It gives the value of the acceleration of an object at each point in time.
Time-derivative  -  The time-derivative of a function is a new function whose value at each point represents the rate of change of the original function with respect to time.
Simple harmonic motion  -  Periodic motion that can be described by special types of position functions. Examples of simple harmonic motion include an object moving in a circle and a ball bouncing up and down on a spring.
Kinematics Formulas

The average velocity for an object with position function x(t) over the time interval (t 0, t 1) .
v avg =

The instantaneous velocity at time t for an object with position function x(t) .
v(t) =
Kinematics Multiple Choice Test
Two birds are flying directly towards each other at the same speed If the first bird is flying at a velocity v , what is the the velocity of the second bird?
(A) v
(B) - v
(C) 2v
(D) Impossible to determine
A United Airlines jet is flying at 300 km/hr, while an Air France Concord is speeding along at 1200 km/hr Both airplanes are flying at the same altitude If each aircraft experiences problems with an unruly passenger, and they both decide simultaneously to push the passenger out the door, which of the unruly passengers will hit the earth first? (Ignore air resistance)
(A) The Air France passenger
(B) The United Airlines passenger
(C) Neither They will both hit the ground at the same time
(D) Impossible to determine The answer depends on which passenger is heavier
Assuming the airplanes in the previous problem continue to travel at the same velocity after ejecting their respective passengers, where will the passengers land with respect to their aircraft's path?
(A) When they hit the ground, they will be directly beneath the airplane they fell from
(B) When they hit the ground, they will be directly beneath the spot at which the airplane threw them out
(C) They will be in front of the aircraft they fell from
(D) It depends on which plane the passenger fell from
The velocity function is all of the following EXCEPT
(A) A function of time
(B) The derivative of the position function
(C) A function which gives the velocity of an object at any point in time
(D) None of the above
A police officer living on a planet with no air resistance drops a pair of handcuffs and a handkerchief from the same height at the same time Which one will reach the ground first?
(A) The handkerchief
(B) The handcuffs
(C) They will both hit the ground at the same time
(D) The answer depends on how far above the ground they were when he dropped them
What kind of function is an acceleration function describing one-dimensional motion?
(A) A scalar-valued function
(B) A vector-valued function
(C) There is no such thing as acceleration in one dimension
(D) A constant function
In general, the acceleration of objects due to the earth's gravitational pull is
(A) constant
(B) 98 m/s 2
(C) smaller if the object is further away
(D) greater if the object is further away
Kinematics is concerned with
(A) understanding why objects move the way they do
(B) describing the movement of objects
(C) action at a distance
(D) None of the above
A raindrop on a drizzly day takes one minute from the time it leaves the cloud until it hits your umbrella, 3 miles below The average velocity of the raindrop on its journey is
(A) 3 miles/hr
(B) 60 miles/hr
(C) 180 miles/hr
(D) Impossible to determine because the raindrop accelerates due to gravity
The average velocity and the instantaneous velocity of an object will be the same if
(A) the object's speed is constant
(B) the object's acceleration is zero
(C) the object's velocity is always positive
(D) They are never the same
A car traveling at constant velocity v suddenly brakes in an effort to keep from hitting a rabbit which is 8 ft away If the braking action causes a constant deceleration a , how long does it take for the car to come to a complete stop?
(A) t = va
(B) t = 8a/v
(C) t = 8a
(D) t = v/a
In the previous question, how far did the car travel as it was braking?
(A)
(B)
(C) 8av
(D) a 2
If the car from the last two questions had initially been traveling at a speed of 10 ft/s, and experienced (from the braking) a deceleration of 5 ft/s 2 , would it have hit the rabbit which was 8 ft away? (Assume the rabbit was dazed and didn't move at all)
(A) yes
(B) no
(C) Impossible to determine without knowing the weight of the car
(D) Impossible to determine because the car can never reach a complete stop
Find the derivative of 2x 5 + x 3 + + 5
(A) 10x 5 + x 2 + 5
(B) 10x 4 + x 2 -
(C) 10x 4 + x 2 + + 5
(D) None of the above
Evaluate the derivative of x 3 + x 2 + 5x at x = - 2
(A) -3
(B) -14
(C) -2
(D) None of the above
Find the velocity of an object described by the position function x(t) = 3x 2 + at time t = - 1
(A) -2
(B) 5
(C) 2
(D) -5
Find the acceleration of an object described by the position function x(t) = 3x 2 + at time t = - 1
(A) -8
(B) 5
(C) 18
(D) None of the above
For the following 5 questions, consider an object with position function x(t) = (0, 0, - g)t 2 + (2, 3, 4)t + (5, 0, 1)
What is the magnitude of the initial (ie at t = 0 ) velocity vector?
(A) 5
(B)
(C)
(D) - g/2
What is the position of the object at time t = - 2 ?
(A) (1, - 6, - 2g - 7)
(B) -12
(C) (1, - 6, - 7)
(D) (0, 0, 0)
The object is moving
(A) in one dimension
(B) in two dimensions
(C) in three dimensions
(D) None of the above
What is the acceleration of this object at time t = 25 ?
(A) - g
(B) 25(0, 0, - g)
(C) g
(D) - (0, 0, g)
This equation might describe an object
(A) in free fall
(B) moving as a projectile
(C) bouncing straight up and down
(D) with changing acceleration
In creature-land, the measure of one's hardcoreness is directly correlated to how high one can jump Unfortunately, creatures cannot jump straight up, but must take a running start If creature A jumps with initial velocity vector (2, 2, 5) , and creature B jumps with initial velocity vector (5, 4, 2) (where the z -direction points upwards), which creature is more hardcore?
(A) creature A
(B) creature B
(C) Both creatures are equally hardcore
(D) Impossible to determine without knowing the gravitational acceleration in creature-land
According to the previous question, which creature travels furthest during its jump?
(A) creature A
(B) creature B
(C) Both creatures land an equal distance away from their starting point
(D) Impossible to determine without knowing the gravitational acceleration in creature-land
Which function could describe the velocity of a ball being thrown horizontally off a fire escape?
(A) v(t) = - (0, 0, g)t 2 + (0, v, 0)t + (0, 0, h)
(B) v(t) = - (0, 0, g)t + (v, 0, 0)t
(C) v(t) = - gt + vt
(D) v(t) = - (0, 0, g)t + (0, 0, v)t
Phin and Wittgenstein are hanging out on the moon when they decide to have a contest to see who can shoot a bullet farther Both use identical guns Phin decides to shoot at a 60 degree angle, while Wittgenstein holds his gun at 45 degrees when shooting Whose bullet lands the furthest away?
(A) Phin's
(B) Wittgenstein's
(C) Both bullets land the same distance away
(D) Impossible to determine without knowing the acceleration due to gravity on the moon
The office of the Harvard Review of Philosophy is located approximately 10 ft below the earth's surface The acceleration due to gravity experienced by members working in this office is
(A) significantly greater than that of people on the earth's surface
(B) significantly smaller than that of people on the earth's surface
(C) approximately equal to that of people on the earth's surface
(D) exactly equal to that of people on the earth's surface
A couple of students at Putney decide to go bicycle riding one day Simon rides at a speed of 10 miles per hour, while Liz's average speed is 20 miles per hour After bicycling for several hours, both Simon and Liz come home and park their bicycles exactly where they started Simons's average velocity for the entire ride is
(A) lower than Liz's average velocity
(B) higher than Liz's average velocity
(C) zero
(D) impossible to determine without knowing the actual directions in which he biked
If, during their bike ride, Simon and Liz were always biking at a constant speed,
(A) their acceleration was always zero
(B) their velocity was constant
(C) their average velocity after one hour of biking was the same as their average velocity after two hours of biking
(D) None of the above
While sitting at his office desk, Stephen Greenblatt enjoys throwing crumpled pieces of paper into a wastebasket across the room Over the years, he has carefully kept track of all the different combinations of initial speeds and angles at which he can throw the crumpled pieces of paper while still making the same basket He hopes to some day have a complete list of all the possibilities Professor Greenblatt's efforts are useless because
(A) although such a list can theoretically be made, he will never have enough time to exhaust all possibilities
(B) there is really only one way to make the basket, and Greenblatt is confused about this because a janitor keeps moving the wastebasket at night
(C) there are infinitely many ways to make this basket from the same position
(D) None of the above
Kinematics Multiple Choice Test
Two birds are flying directly towards each other at the same speed If the first bird is flying at a velocity v , what is the the velocity of the second bird?
(A) v
(B) - v
(C) 2v
(D) Impossible to determine
A United Airlines jet is flying at 300 km/hr, while an Air France Concord is speeding along at 1200 km/hr Both airplanes are flying at the same altitude If each aircraft experiences problems with an unruly passenger, and they both decide simultaneously to push the passenger out the door, which of the unruly passengers will hit the earth first? (Ignore air resistance)
(A) The Air France passenger
(B) The United Airlines passenger
(C) Neither They will both hit the ground at the same time
(D) Impossible to determine The answer depends on which passenger is heavier
Assuming the airplanes in the previous problem continue to travel at the same velocity after ejecting their respective passengers, where will the passengers land with respect to their aircraft's path?
(A) When they hit the ground, they will be directly beneath the airplane they fell from
(B) When they hit the ground, they will be directly beneath the spot at which the airplane threw them out
(C) They will be in front of the aircraft they fell from
(D) It depends on which plane the passenger fell from
The velocity function is all of the following EXCEPT
(A) A function of time
(B) The derivative of the position function
(C) A function which gives the velocity of an object at any point in time
(D) None of the above
A police officer living on a planet with no air resistance drops a pair of handcuffs and a handkerchief from the same height at the same time Which one will reach the ground first?
(A) The handkerchief
(B) The handcuffs
(C) They will both hit the ground at the same time
(D) The answer depends on how far above the ground they were when he dropped them
What kind of function is an acceleration function describing one-dimensional motion?
(A) A scalar-valued function
(B) A vector-valued function
(C) There is no such thing as acceleration in one dimension
(D) A constant function
In general, the acceleration of objects due to the earth's gravitational pull is
(A) constant
(B) 98 m/s 2
(C) smaller if the object is further away
(D) greater if the object is further away
Kinematics is concerned with
(A) understanding why objects move the way they do
(B) describing the movement of objects
(C) action at a distance
(D) None of the above
A raindrop on a drizzly day takes one minute from the time it leaves the cloud until it hits your umbrella, 3 miles below The average velocity of the raindrop on its journey is
(A) 3 miles/hr
(B) 60 miles/hr
(C) 180 miles/hr
(D) Impossible to determine because the raindrop accelerates due to gravity
The average velocity and the instantaneous velocity of an object will be the same if
(A) the object's speed is constant
(B) the object's acceleration is zero
(C) the object's velocity is always positive
(D) They are never the same
A car traveling at constant velocity v suddenly brakes in an effort to keep from hitting a rabbit which is 8 ft away If the braking action causes a constant deceleration a , how long does it take for the car to come to a complete stop?
(A) t = va
(B) t = 8a/v
(C) t = 8a
(D) t = v/a
In the previous question, how far did the car travel as it was braking?
(A)
(B)
(C) 8av
(D) a 2
If the car from the last two questions had initially been traveling at a speed of 10 ft/s, and experienced (from the braking) a deceleration of 5 ft/s 2 , would it have hit the rabbit which was 8 ft away? (Assume the rabbit was dazed and didn't move at all)
(A) yes
(B) no
(C) Impossible to determine without knowing the weight of the car
(D) Impossible to determine because the car can never reach a complete stop
Find the derivative of 2x 5 + x 3 + + 5
(A) 10x 5 + x 2 + 5
(B) 10x 4 + x 2 -
(C) 10x 4 + x 2 + + 5
(D) None of the above
Evaluate the derivative of x 3 + x 2 + 5x at x = - 2
(A) -3
(B) -14
(C) -2
(D) None of the above
Find the velocity of an object described by the position function x(t) = 3x 2 + at time t = - 1
(A) -2
(B) 5
(C) 2
(D) -5
Find the acceleration of an object described by the position function x(t) = 3x 2 + at time t = - 1
(A) -8
(B) 5
(C) 18
(D) None of the above
For the following 5 questions, consider an object with position function x(t) = (0, 0, - g)t 2 + (2, 3, 4)t + (5, 0, 1)
What is the magnitude of the initial (ie at t = 0 ) velocity vector?
(A) 5
(B)
(C)
(D) - g/2
What is the position of the object at time t = - 2 ?
(A) (1, - 6, - 2g - 7)
(B) -12
(C) (1, - 6, - 7)
(D) (0, 0, 0)
The object is moving
(A) in one dimension
(B) in two dimensions
(C) in three dimensions
(D) None of the above
What is the acceleration of this object at time t = 25 ?
(A) - g
(B) 25(0, 0, - g)
(C) g
(D) - (0, 0, g)
This equation might describe an object
(A) in free fall
(B) moving as a projectile
(C) bouncing straight up and down
(D) with changing acceleration
In creature-land, the measure of one's hardcoreness is directly correlated to how high one can jump Unfortunately, creatures cannot jump straight up, but must take a running start If creature A jumps with initial velocity vector (2, 2, 5) , and creature B jumps with initial velocity vector (5, 4, 2) (where the z -direction points upwards), which creature is more hardcore?
(A) creature A
(B) creature B
(C) Both creatures are equally hardcore
(D) Impossible to determine without knowing the gravitational acceleration in creature-land
According to the previous question, which creature travels furthest during its jump?
(A) creature A
(B) creature B
(C) Both creatures land an equal distance away from their starting point
(D) Impossible to determine without knowing the gravitational acceleration in creature-land
Which function could describe the velocity of a ball being thrown horizontally off a fire escape?
(A) v(t) = - (0, 0, g)t 2 + (0, v, 0)t + (0, 0, h)
(B) v(t) = - (0, 0, g)t + (v, 0, 0)t
(C) v(t) = - gt + vt
(D) v(t) = - (0, 0, g)t + (0, 0, v)t
Phin and Wittgenstein are hanging out on the moon when they decide to have a contest to see who can shoot a bullet farther Both use identical guns Phin decides to shoot at a 60 degree angle, while Wittgenstein holds his gun at 45 degrees when shooting Whose bullet lands the furthest away?
(A) Phin's
(B) Wittgenstein's
(C) Both bullets land the same distance away
(D) Impossible to determine without knowing the acceleration due to gravity on the moon
The office of the Harvard Review of Philosophy is located approximately 10 ft below the earth's surface The acceleration due to gravity experienced by members working in this office is
(A) significantly greater than that of people on the earth's surface
(B) significantly smaller than that of people on the earth's surface
(C) approximately equal to that of people on the earth's surface
(D) exactly equal to that of people on the earth's surface
A couple of students at Putney decide to go bicycle riding one day Simon rides at a speed of 10 miles per hour, while Liz's average speed is 20 miles per hour After bicycling for several hours, both Simon and Liz come home and park their bicycles exactly where they started Simons's average velocity for the entire ride is
(A) lower than Liz's average velocity
(B) higher than Liz's average velocity
(C) zero
(D) impossible to determine without knowing the actual directions in which he biked
If, during their bike ride, Simon and Liz were always biking at a constant speed,
(A) their acceleration was always zero
(B) their velocity was constant
(C) their average velocity after one hour of biking was the same as their average velocity after two hours of biking
(D) None of the above
While sitting at his office desk, Stephen Greenblatt enjoys throwing crumpled pieces of paper into a wastebasket across the room Over the years, he has carefully kept track of all the different combinations of initial speeds and angles at which he can throw the crumpled pieces of paper while still making the same basket He hopes to some day have a complete list of all the possibilities Professor Greenblatt's efforts are useless because
(A) although such a list can theoretically be made, he will never have enough time to exhaust all possibilities
(B) there is really only one way to make the basket, and Greenblatt is confused about this because a janitor keeps moving the wastebasket at night
(C) there are infinitely many ways to make this basket from the same position
(D) None of the above
Review Test
Who provided a basis for the study of dynamics?
(A) Galileo
(B) Newton
(C) Kepler
(D) Einstein
What are the units of force, in terms of fundamental units?
(A)
(B) Newtons
(C)
(D) kg·m
Inertia is the tendency of an object to remain at constant
(A) Acceleration
(B) Position
(C) Speed
(D) Velocity
Which of the following constitutes an inertial reference frame?
(A) A satellite in orbit
(B) An object moving in uniform circular motion
(C) A car moving with constant velocity
(D) An object in free fall
What is the weight on earth of a 50 kg person?
(A) 490 N
(B) 9.8 N
(C) 50 N
(D) Not enough information
What is the weight of a 50 kg person in outer space?
(A) 490 N
(B) 50 N
(C) O N
(D) Not enough information
In what way are force and acceleration related?
(A) Inversely proportional
(B) Directly proportional
(C) F is proportional to a 2
(D) There is no relation
A 10 kg mass experiences a force of 20 N. What is its acceleration?
(A) 2 m/s
(B) 200 m/s
(C) 0.5 m/s
(D) 20 m/s
An object with mass 2 kg moves with a velocity of 10 m/s. What is the net force on the body?
(A) 20 N
(B) 0 N
(C) 5 N
(D) 20 N
What are the units of weight, in terms of fundamental units?
(A)
(B) Newtons
(C)
(D) kg
An object of mass 1 kg experiences two equal and opposite forces, each of 10 N. What is its acceleration?
(A) 20 m/s 2
(B) 10 m/s 2
(C) 0
(D) 12 N
A force of 3 N and a force of 4 N act together to produce a resultant force of 5 N. What must be the angle between them?
(A) 0
(B) 90
(C) 180
(D) Not enough information
The net force from two distinct forces is at a maximum when the angle between them is
(A) 0
(B) 45
(C) 180
(D) 90
Three forces, each separated from one another by 120 o yield a net force of 0. What can be said about the magnitude of the forces?
(A) They add to 0
(B) The sum of the magnitude of two forces must equal the magnitude of the third force
(C) They are all equal
(D) Not enough information
An object is said to be at equilibrium if
(A) It is moving at constant velocity
(B) It is moving at constant acceleration
(C) No forces act upon it
(D) No net force acts upon it
A man pushes on a 10 kg crate with a force of 50 N. What force does the man experience?
(A) 50 N
(B) 500 N
(C) 5 N
(D) 0 N
What is constant for a freely falling object?
(A) Velocity
(B) Position
(C) Speed
(D) Acceleration
The acceleration due to gravity on the moon is 1/6 the value of that on earth. What is the weight of a 100 kg man on the moon?
(A) 163 N
(B) 100 N
(C) 17 N
(D) 238 N
Which of Newton's Laws relate the force of two mutually interacting bodies?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Which of Newton's Laws define the concept of inertia?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Two surfaces are in contact. The normal force between them always points
(A) Vertically
(B) Perpendicular to the plane of contact
(C) Horizontally
(D) Parallel to the plane of contact
A 10 kg mass rests on an inclined plane with angle of elevation of θ . What is the magnitude of the normal force?
(A) 98 N
(B) 10 N
(C) 98 sinθ N
(D) 98 cosθ N
The normal force is a direct consequence of which of Newton's Laws?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Frictional force is the result of what kind of fundamental force?
(A) Gravitational Force
(B) Nuclear Force
(C) Normal Force
(D) Electrical Force
Frictional force always acts in what direction relative to the motion of one body relative to the other?
(A) In the opposite direction as the motion of the body it is being acted upon.
(B) Perpendicular to the plane of motion
(C) In the same direction as the motion of the body it is being acted upon.
(D) Horizontally
A 10 kg block is at rest on a horizontal table. The coefficient of static friction between them is .5. What is the frictional force acting upon the block?
(A) 49 N
(B) 5 N
(C) 0 N
(D) 98 N
A 10 kg block lies at rest on a table, with a coefficient of static friction between them of .5. A horizontal force is then applied of magnitude 50 N. What is the frictional force acting upon the block after the force is applied?
(A) 48 N
(B) 0 N
(C) 98 N
(D) Not enough information
The coefficient of static friction is related to the coefficient of kinetic friction in what way?
(A) The coefficient of static friction is always less than the coefficient of kinetic friction
(B) They are equal
(C) The coefficient of static friction is always greater than the coefficient of kinetic friction
(D) Not enough information
A block moves across a tabletop with a certain speed and experiences a kinetic frictional force. What happens to the frictional force when the speed of the block is doubled?
(A) The force is doubled
(B) The force is quadrupled
(C) The force is halved
(D) The force remains the same
A 10 kg block lies at rest on table. The coefficient of static friction and the coefficient of kinetic friction between the block and the table are .5 and .25 respectively. A 50 N force is applied horizontally to the block. What is the magnitude of the frictional force applied to the block?
(A) 24.5 N
(B) 49 N
(C) 50 N
(D) 0 N
See the above problem. What is the acceleration of the block while the force is being applied, in m/s 2 ?
(A) .1
(B) 2.55
(C) 5
(D) 2.45
Kinetic frictional force is always directly proportional to what other force?
(A) Electrical force
(B) Gravitational Force
(C) Tension Force
(D) Normal Force
A 2 kg block is moving with constant velocity across a table with a coefficient of kinetic friction of .5. How much external force is being applied to the block?
(A) 9.8 N
(B) O N
(C) 18 N
(D) 24.5 N
The net force on a massless rope is always
(A) The vector sum of the tension on the rope.
(B) 9.8 N
(C) 0 N
(D) Not enough information
A 10 kg block is held in equilibrium by a rope hanging vertically from the ceiling. What is the tension in the rope?
(A) 10 N
(B) 49 N
(C) 5 N
(D) 98 N
A man attaches a rope to a 20 kg block, pulling it across a floor with constant velocity. The coefficient of kinetic friction between the block and the floor is .5. What is the tension in the rope?
(A) 98 N
(B) 196 N
(C) 20 N
(D) Not enough information
A cube has sides of area 2 cm 2 , 3 cm 2 and 4 cm 2 . What side of the cube will experience the least friction when moved across a rough surface?
(A) The 2 cm 2 side
(B) The 3 cm 2 side
(C) The 4 cm 2 side
(D) Each side experiences the same amount of friction.
A 10 kg block is placed on a floor, but attached to a rope via a pulley system. A person pulls on the rope until the tension in the rope is 90 N. What is the normal force exerted by the floor at this point?
(A) 0 N
(B) 98 N
(C) 8 N
(D) 106 N
If the normal force between two surfaces is doubled, the coefficient of static friction will
(A) Double
(B) Be halved
(C) Remain the same
(D) Quadruple
A 10 kg block is pushed horizontally against a vertical wall, with coefficient of static friction of .25 between the block and the wall. With what force must the block be pushed against the wall in order to keep the block from falling?
(A) 24.5 N
(B) 392 N
(C) 49 N
(D) 98 N
When traveling in uniform circular motion, all of the following stay constant EXCEPT
(A) Speed
(B) Acceleration
(C) Radius
(D) Velocity
When moving in uniform circular motion, the acceleration of a particle is always
(A) Directed toward the center of the circle
(B) Proportional to the velocity of the particle
(C) Proportional to the radius of the circle
(D) Directed away from the center of the circle
A particle is accelerated in uniform circular motion at a rate of 2 m/s 2 , around a circle of radius of 18 m. What is the particle's speed, in m/s?
(A) 36
(B) 9
(C) 6
(D) 3
A 10 m rope has a maximum tension of 20 N. What is the most mass it can keep in uniform circular motion at a velocity of 10 m/s?
(A) 2 kg
(B) 20 kg
(C) 10 kg
(D) 100 kg
Centripetal force always points in what direction?
(A) Tangential to the circle
(B) Away from the center of the circle
(C) Toward the center of the circle
(D) Perpendicular to the plane of the circle
When a car goes around a curve, the centripetal force is provided by
(A) The normal force
(B) The kinetic frictional force
(C) The gravitational force
(D) The static frictional force
Which of the following is NOT an example of uniform circular motion?
(A) A planet orbiting the sun
(B) The earth rotating about its axis
(C) A cylinder rolling down an incline
(D) A car going around a curve at constant velocity
How much must the centripetal force change if the speed around a circle is doubled?
(A) It must be doubled
(B) It must be quadrupled
(C) It must be halved
(D) It must stay the same
How much must the centripetal force change if the radius of the circle is doubled?
(A) It must be doubled
(B) It must be quadrupled
(C) It must be halved
(D) It must stay the same
Which of Newton's Laws do NOT apply to uniform circular motion?
(A) 1st
(B) 2nd
(C) 3rd
(D) None of the above
Review Test
Who provided a basis for the study of dynamics?
(A) Galileo
(B) Newton
(C) Kepler
(D) Einstein
What are the units of force, in terms of fundamental units?
(A)
(B) Newtons
(C)
(D) kg·m
Inertia is the tendency of an object to remain at constant
(A) Acceleration
(B) Position
(C) Speed
(D) Velocity
Which of the following constitutes an inertial reference frame?
(A) A satellite in orbit
(B) An object moving in uniform circular motion
(C) A car moving with constant velocity
(D) An object in free fall
What is the weight on earth of a 50 kg person?
(A) 490 N
(B) 9.8 N
(C) 50 N
(D) Not enough information
What is the weight of a 50 kg person in outer space?
(A) 490 N
(B) 50 N
(C) O N
(D) Not enough information
In what way are force and acceleration related?
(A) Inversely proportional
(B) Directly proportional
(C) F is proportional to a 2
(D) There is no relation
A 10 kg mass experiences a force of 20 N. What is its acceleration?
(A) 2 m/s
(B) 200 m/s
(C) 0.5 m/s
(D) 20 m/s
An object with mass 2 kg moves with a velocity of 10 m/s. What is the net force on the body?
(A) 20 N
(B) 0 N
(C) 5 N
(D) 20 N
What are the units of weight, in terms of fundamental units?
(A)
(B) Newtons
(C)
(D) kg
An object of mass 1 kg experiences two equal and opposite forces, each of 10 N. What is its acceleration?
(A) 20 m/s 2
(B) 10 m/s 2
(C) 0
(D) 12 N
A force of 3 N and a force of 4 N act together to produce a resultant force of 5 N. What must be the angle between them?
(A) 0
(B) 90
(C) 180
(D) Not enough information
The net force from two distinct forces is at a maximum when the angle between them is
(A) 0
(B) 45
(C) 180
(D) 90
Three forces, each separated from one another by 120 o yield a net force of 0. What can be said about the magnitude of the forces?
(A) They add to 0
(B) The sum of the magnitude of two forces must equal the magnitude of the third force
(C) They are all equal
(D) Not enough information
An object is said to be at equilibrium if
(A) It is moving at constant velocity
(B) It is moving at constant acceleration
(C) No forces act upon it
(D) No net force acts upon it
A man pushes on a 10 kg crate with a force of 50 N. What force does the man experience?
(A) 50 N
(B) 500 N
(C) 5 N
(D) 0 N
What is constant for a freely falling object?
(A) Velocity
(B) Position
(C) Speed
(D) Acceleration
The acceleration due to gravity on the moon is 1/6 the value of that on earth. What is the weight of a 100 kg man on the moon?
(A) 163 N
(B) 100 N
(C) 17 N
(D) 238 N
Which of Newton's Laws relate the force of two mutually interacting bodies?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Which of Newton's Laws define the concept of inertia?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Two surfaces are in contact. The normal force between them always points
(A) Vertically
(B) Perpendicular to the plane of contact
(C) Horizontally
(D) Parallel to the plane of contact
A 10 kg mass rests on an inclined plane with angle of elevation of θ . What is the magnitude of the normal force?
(A) 98 N
(B) 10 N
(C) 98 sinθ N
(D) 98 cosθ N
The normal force is a direct consequence of which of Newton's Laws?
(A) 1st
(B) 2nd
(C) 3rd
(D) 4th
Frictional force is the result of what kind of fundamental force?
(A) Gravitational Force
(B) Nuclear Force
(C) Normal Force
(D) Electrical Force
Frictional force always acts in what direction relative to the motion of one body relative to the other?
(A) In the opposite direction as the motion of the body it is being acted upon.
(B) Perpendicular to the plane of motion
(C) In the same direction as the motion of the body it is being acted upon.
(D) Horizontally
A 10 kg block is at rest on a horizontal table. The coefficient of static friction between them is .5. What is the frictional force acting upon the block?
(A) 49 N
(B) 5 N
(C) 0 N
(D) 98 N
A 10 kg block lies at rest on a table, with a coefficient of static friction between them of .5. A horizontal force is then applied of magnitude 50 N. What is the frictional force acting upon the block after the force is applied?
(A) 48 N
(B) 0 N
(C) 98 N
(D) Not enough information
The coefficient of static friction is related to the coefficient of kinetic friction in what way?
(A) The coefficient of static friction is always less than the coefficient of kinetic friction
(B) They are equal
(C) The coefficient of static friction is always greater than the coefficient of kinetic friction
(D) Not enough information
A block moves across a tabletop with a certain speed and experiences a kinetic frictional force. What happens to the frictional force when the speed of the block is doubled?
(A) The force is doubled
(B) The force is quadrupled
(C) The force is halved
(D) The force remains the same
A 10 kg block lies at rest on table. The coefficient of static friction and the coefficient of kinetic friction between the block and the table are .5 and .25 respectively. A 50 N force is applied horizontally to the block. What is the magnitude of the frictional force applied to the block?
(A) 24.5 N
(B) 49 N
(C) 50 N
(D) 0 N
See the above problem. What is the acceleration of the block while the force is being applied, in m/s 2 ?
(A) .1
(B) 2.55
(C) 5
(D) 2.45
Kinetic frictional force is always directly proportional to what other force?
(A) Electrical force
(B) Gravitational Force
(C) Tension Force
(D) Normal Force
A 2 kg block is moving with constant velocity across a table with a coefficient of kinetic friction of .5. How much external force is being applied to the block?
(A) 9.8 N
(B) O N
(C) 18 N
(D) 24.5 N
The net force on a massless rope is always
(A) The vector sum of the tension on the rope.
(B) 9.8 N
(C) 0 N
(D) Not enough information
A 10 kg block is held in equilibrium by a rope hanging vertically from the ceiling. What is the tension in the rope?
(A) 10 N
(B) 49 N
(C) 5 N
(D) 98 N
A man attaches a rope to a 20 kg block, pulling it across a floor with constant velocity. The coefficient of kinetic friction between the block and the floor is .5. What is the tension in the rope?
(A) 98 N
(B) 196 N
(C) 20 N
(D) Not enough information
A cube has sides of area 2 cm 2 , 3 cm 2 and 4 cm 2 . What side of the cube will experience the least friction when moved across a rough surface?
(A) The 2 cm 2 side
(B) The 3 cm 2 side
(C) The 4 cm 2 side
(D) Each side experiences the same amount of friction.
A 10 kg block is placed on a floor, but attached to a rope via a pulley system. A person pulls on the rope until the tension in the rope is 90 N. What is the normal force exerted by the floor at this point?
(A) 0 N
(B) 98 N
(C) 8 N
(D) 106 N
If the normal force between two surfaces is doubled, the coefficient of static friction will
(A) Double
(B) Be halved
(C) Remain the same
(D) Quadruple
A 10 kg block is pushed horizontally against a vertical wall, with coefficient of static friction of .25 between the block and the wall. With what force must the block be pushed against the wall in order to keep the block from falling?
(A) 24.5 N
(B) 392 N
(C) 49 N
(D) 98 N
When traveling in uniform circular motion, all of the following stay constant EXCEPT
(A) Speed
(B) Acceleration
(C) Radius
(D) Velocity
When moving in uniform circular motion, the acceleration of a particle is always
(A) Directed toward the center of the circle
(B) Proportional to the velocity of the particle
(C) Proportional to the radius of the circle
(D) Directed away from the center of the circle
A particle is accelerated in uniform circular motion at a rate of 2 m/s 2 , around a circle of radius of 18 m. What is the particle's speed, in m/s?
(A) 36
(B) 9
(C) 6
(D) 3
A 10 m rope has a maximum tension of 20 N. What is the most mass it can keep in uniform circular motion at a velocity of 10 m/s?
(A) 2 kg
(B) 20 kg
(C) 10 kg
(D) 100 kg
Centripetal force always points in what direction?
(A) Tangential to the circle
(B) Away from the center of the circle
(C) Toward the center of the circle
(D) Perpendicular to the plane of the circle
When a car goes around a curve, the centripetal force is provided by
(A) The normal force
(B) The kinetic frictional force
(C) The gravitational force
(D) The static frictional force
Which of the following is NOT an example of uniform circular motion?
(A) A planet orbiting the sun
(B) The earth rotating about its axis
(C) A cylinder rolling down an incline
(D) A car going around a curve at constant velocity
How much must the centripetal force change if the speed around a circle is doubled?
(A) It must be doubled
(B) It must be quadrupled
(C) It must be halved
(D) It must stay the same
How much must the centripetal force change if the radius of the circle is doubled?
(A) It must be doubled
(B) It must be quadrupled
(C) It must be halved
(D) It must stay the same
Which of Newton's Laws do NOT apply to uniform circular motion?
(A) 1st
(B) 2nd
(C) 3rd
(D) None of the above