Physics Exam 3 Questions

A wheel with a 0.10-m radius is rotating at 35 rev/s. It then slows uniformly to 15 rev/s over a 3.0-s interval. What is the angular acceleration of a point on the wheel?

-6.7 rev/s2

A stock person at the local grocery store has a job consisting of the following five segments: (1) picking up boxes of tomatoes from the stockroom floor (2) accelerating to a comfortable speed (3) carrying the boxes to the tomato display at constant speed (4) decelerating to a stop (5) lowering the boxes slowly to the floor. During which of the five segments of the job does the stock person do positive work on the boxes?

1) Picking up boxes of tomatoes from the stockroom floor 2) Accelerating to a comfortable speed

John's mass is half the mass of Jill. They both start walking and John moves twice as fast as Jill. What is the ratio of the kinetic energy of Jill to the kinetic energy of John? a) 1/8 b) 1/2 c) 4 d) 2

1/2

A fan rotating with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, how many revolutions does the blade undergo during this time?

20

Rank the change in kinetic energy from the smallest change to the largest change: 1. A car's speed changes from 15 m/s to 20 m/s. 2. A car's speed changes from 20 m/s to 25 m/s. 3. A car's speed changes from 5 m/s to 10 m/s. 4. A car's speed changes from 25 m/s to 28 m/s.

3,4,1,2

An object hits a wall and bounces back with half of its original speed. What is the ratio of the initial kinetic energy to the final kinetic energy? a) 2 b) 1/2 c)1/4 d) 4

4

Two uniform solid spheres have the same mass, but one has twice the radius of the other. The ratio of the larger sphere's moment of inertia to that of the smaller sphere is

4

A 0.200-kg mass hangs from the end of a vertical spring causing it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the spring will be a) half as much b) 4 times as much c) the same d) twice as much

4 times as much

What is the tangential speed of a lug nut on a wheel of a car if the lug nut is located 0.114 m from the axis of rotation; and the wheel is rotating at 6.53 rev/sec?

4.68 m/s

A block of mass m is pushed against a spring of spring constant k. The spring is compressed by a distance d, the block is then released. It is launched by the spring along a horizontal frictionless surface with a final speed v. A second block, this one having mass 4m is pushed against the same spring and released, gaining a final speed 2v. By what distance was the spring compressed in the second case? a) 16d b) 4d c) 25d d) d

4d

In which one of the following systems is there an increase in gravitational potential energy? a) My cat Yadi patiently waits on the floor by his food bowl for dinner. b) A truck drives at an average velocity of 25 m/s, due north along a level, county road. c) My cat Yadi jumps down from a bed and lands on his feet. d) A child accidentally releases a helium-filled balloon and it flies upward toward the clouds.

A child accidentally releases a helium-filled balloon and it flies upward toward the clouds.

Which of the following statements is true? a) all of these b) The work done by a conservative force depends on the path taken. c)A conservative force permits a two-way conversion between kinetic and potential energies. d) A potential energy function can be specified for a nonconservative force.

A conservative force permits a two-way conversion between kinetic and potential energies.

Block 1 and block 2 have the same mass, m, and are released from the top of two inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. If the coefficient of friction is the same in both cases, which of the blocks is going faster when it reaches the bottom of its respective incline?

Block 2 is faster

Two blocks of masses m1 and m2 are released from the top of two frictionless inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively. Which of the blocks is going faster when it reaches the bottom of its respective incline?

Both blocks have the same speed at the bottom.

You and your friend want to go to the top of the Empire State Building. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy (U) of you and your friend, after you both reach the top. Assume you have the same mass.

Both of you have the same amount of potential energy.

An airplane starts from rest at the end of a runway and begins accelerating. The tires of the plane are rotating with an angular velocity that is uniformly increasing with time. On one of the tires, Point A is located on the part of the tire in contact with the runway surface and point B is located halfway between Point A and the axis of rotation. Which one of the following statements is true concerning this situation?

Both points have the same instantaneous velocity.

A girl and a boy are riding on a merry-go-round that is turning at a constant rate. The girl is near the outer edge, and the boy is closer to the center. Who has smaller angular displacement?

Both the girl and the boy have the same nonzero angular displacement.

Two children are riding on a merry-go-round. Child A is at a greater distance from the axis of rotation than child B. Which child has the greater linear displacement?

Child A

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to maximize your speed on the skateboard?

Deflect the ball

Which of the following is false regarding energy? a)Energy can be transferred. b) Energy can be created. c) Energy is conserved. d) Energy is conserved.

Energy can be created

A boy and a girl are riding on a merry-go-round that is turning. The boy is twice as far as the girl from the merry-go-round's center. If the boy and girl are of equal mass, which statement is true about the boy's moment of inertia with respect to the axis of rotation?

His moment of inertia is 4 times the girl's.

Two football players, Ted and Jeff, with the same weight are climbing steps during practice. Ted completes one set of steps in 30 seconds, Jeff completes two sets of steps in 60 seconds. How does the power used by each player compare? a) Jeff and Ted use the same amount of power b) Ted uses less power because his total time is less than Jeff's total time c) Ted uses more power because he climbs one set of steps while Jeff climbs two sets of steps d) Jeff uses more power because he does more work

Jeff and Ted use the same amount of power

An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U. a) K decreases and U increases b) K increases and U increases c) K increases and U decreases d) K decreases and U decreases

K increases and U decreases

A truck has four times the mass of a car and is moving with twice the speed of the car. If Kt and Kc refer to the kinetic energies of truck and car respectively, it is correct to say that a) Kt=16Kc b)Kt=Kc c) Kt=4Kc d)Kt=2Kc

Kt=16Kc

Power may be expressed using all of the following units except: a) Watt b)Joules/ second c)N*m*s d) all of these are units of power

N*m*s

A ping-pong ball moving east at a speed of 4 m/s, collides with a stationary bowling ball. The Ping-Pong ball bounces back to the west, and the bowling ball moves very slowly to the east. Which object experiences the greater magnitude impulse during the collision?

Neither; both experienced the same magnitude impulse.

Jacques and George meet in the middle of a lake while paddling in their canoes. They come to a complete stop and talk for a while. When they are ready to leave, Jacques pushes George's canoe with a force to separate the two canoes. What is correct to say about the final momentum and kinetic energy of the system?

The final momentum is zero kg∙m/s but the final kinetic energy is positive.

Starting from rest, a solid sphere rolls without slipping down an incline plane. At the bottom of the incline, what does the angular velocity of the sphere depend upon?

The angular velocity depends upon the height of the incline.

A stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following best describes why no injury occurs?

The bag increases the amount of time during which the momentum is changing and reduces the average force on the person.

In a lab environment, you are investigating the impulse of a force exerted on a brick when the brick's speed is reduced from 2.5 m/s to a complete stop. First, you allow the brick to slam into a secured piece of wood, bringing the brick to a sudden stop. Second, you allow the brick to plow into a large slab of gelatin so that the brick comes to a gradual halt. In which situation is there a greater impulse of the force on the brick? a) There is a greater impulse of the force on the brick from the wall. b) Not enough information is given to determine the answer. c) There is a greater impulse of the force on the brick from the gelatin. d) The impulse is the same in both situations.

The impulse is the same in both situations.

Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare?

The maximum height of the second ball is four times that of the first ball.

Which of the following statements about the moment of inertia is false? a)Of the particles that make up an object, the particle with the smallest mass may contribute the greatest amount to the moment of inertia. b) The moment of inertia depends on the angular acceleration of the object as it rotates. c)The moment of inertia depends on the orientation of the rotation axis relative to the particles that make up the object. d)The moment of inertia depends on the location of the rotation axis relative to the particles that make up the object.

The moment of inertia depends on the angular acceleration of the object as it rotates.

A freight car moves along a frictionless level railroad track at constant speed. The freight car is open on the top. A large load of sand is suddenly dumped into the freight car. What happens to the speed of the freight car?

The speed of the freight car decreases.

A collision between two objects is elastic. Which one of the following statements concerning this situation is true? a) The total momentum of the objects is zero kg*m/s after the collision. b) The total kinetic energy of the objects is the same before and after the collision. c) The vector sum of the velocities of the two objects is equal to zero m/s after the collision. d) The objects stick together and move as one after the collision.

The total kinetic energy of the objects is the same before and after the collision.

An object is rolling, so its motion involves both rotation and translation. Which of the following statements must be true concerning this situation? a)The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object. b)The gravitational potential energy must be changing as the object rolls. c) The rotational kinetic energy must be constant as the object rolls. d) The translational kinetic energy may be 0 joules.

The total mechanical energy is equal to the sum of the translational and rotational kinetic energies and the gravitational potential energy of the object.

An artillery shell explodes in midair and breaks up into many fragments. Which of the following statements are true regarding conditions immediately before and immediately after the explosion: I. The total momentum of the fragments is equal to the original momentum of the shell. II. The total kinetic energy of the fragments is equal to the original kinetic energy of the shell.

The total momentum of the fragments is equal to the original momentum of the shell.

When a person steps forward out of a small boat onto a dock, the boat recoils backward in the water. Why does this occur?

The total momentum of the system is conserved.

Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height?

The two objects rise to the same height.

An inelastic collision of two objects is characterized by the following.

Total momentum of the system remains constant.

Consider a solid sphere of radius R and mass M rolling without slipping. Which form of kinetic energy is larger, translational or rotational?

Translational kinetic energy is larger.

A car originally at rest has its speed increased to a value v in a period of 5 seconds. The work performed in this part of the motion is W1. Over the next 5 seconds the speed of the car is increased to 2v. In the second part of the motion the work performed is W2. It is correct to say that: a) W2= 4W1 b) W2=2W1 c)W2=(1/2)W1 d)W2=3W1

W2=3W1

You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. a) Work is positive on the way up and positive on the way down b) Work is negative on the way up and negative on the way down c) Work is negative on the way up and positive on the way down d)Work is positive on the way up and negative on the way down

Work is negative on the way up and positive on the way down

Complete the following statement: A force that acts on an object is said to be conservative if a) the work it does can be stored in a form of energy that can be released later b) the work it does on the object is independent of the path of the motion c) if the work it does on a closed path is zero d) all of these

all of these

Which one of the following provides a basis to distinguish different types of collisions? a) conservation of linear momentum b) conservation of kinetic energy c) conservation of mass d) conservation of impulse

conservation of kinetic energy

As compared to Jack, Jill does twice the work in half the time. Jill's power output is a) one half as much as Jack's power input b) four times Jack's output c) twice Jack's power output d) the same as jack's power output

four times Jack's output

Complete the following statement: The change in momentum with respect to time for an object a) is equal in magnitude to the net force acting on the object, but opposite in direction. b) has a constant value if the force acting on the object is conservative. c)is a scalar quantity that may be negative, zero, or positive. d) is always positive

has a constant value if the force acting on the object is conservative.

The total mechanical energy of a system

is constant, only if conservative forces act.

If you push twice as hard against a stationary brick wall, the amount of work you do a) remains constant but non-zero b) quadruples c) doubles d) remains constant but zero

remains constant but zero

If the net work done on an object is zero, then the object's kinetic energy a) increases b) decreases c) remains zero d) remains the same

remains the same

Two pucks on an air hockey table collide elastically. Complete the following statement: when such a collision occurs in two dimensions, the before and after velocities are best determined by

remembering the momentum is a vector quantity that is conserved in each direction.

A disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They all roll without slipping. In what order do they reach the bottom?

sphere, disk, hoop

Rolling without slipping depends on

static friction between the rolling object and the ground.

If the slope of the curve on a potential energy versus position graph is positive, what can we say about the force? a) the force is zero b) the force is positive c) the force is negative d) force cannot be determined by a potential energy vs position graph

the force is negative

Complete the following statement: The center of mass is a) the point at the geometrical center of an object. b)the region of an object where most of the mass is located c) the point within an object that moves as if all of the object's mass were located there. d) the only point on an object at which the gravitational force acts.

the point within an object that moves as if all of the object's mass were located there.

A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which object experiences the lessor momentum change?

the putty

Complete the following statement: For a wheel that turns with constant angular speed,

the wheel turns through "equal angles in equal times."

On a force vs. position graph, the area under curve is a representation of a)position b)work c)force d) acceleration

work

Work done by STATIC FRICTION is always a) zero b) perpendicular to the surface c) negative d) parallel to the surface

zero