Physics Exam 2

Which of the following statements is/are true? Check all that apply. a. The total mechanical energy of a system is equally divided between kinetic and potential energy. b. Mechanical energy can be dissipated to nonmechanical forms of energy. c. The total mechanical energy of a system is constant only if conservative forces do work. d. The total mechanical energy of a system is constant only if nonconservative forces do work. e. The total mechanical energy of a system, at any one instant, is either all kinetic or all potential energy.

B,C

A constant net torque is applied to a rotating object. Which of the following best describes the object's motion? a. The object will rotate with constant angular velocity. b. The object will rotate with increasing angular acceleration. c. The object will rotate with constant angular acceleration. d. The object will have an increasing moment of inertia. e. The object will have a decreasing moment of inertia. f. The object will rotate with decreasing angular acceleration.

C

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 greater angular displacement? a, The girl has greater angular displacement. b. Both the girl and the boy have zero angular displacement. c. Both the girl and the boy have the same nonzero angular displacement. d. The boy has greater angular displacement.

C

A girl spins around in a circle trying to make herself dizzy. Without changing her position, she starts spinning twice as fast. By how much did her rotational kinetic energy change? a. It did not change. b. It halved. c. It quadrupled. d. It doubled.

C

A graph depicts force versus position. What represents the work done by the force over the given displacement? a. Work cannot be determined from this type of graph. b. The work done is equal to length of the curve. c. The work done is equal to the area under the curve. d. The work done is equal to the product of the maximum force times the maximum position. e. The work done is equal to the slope of the curve.

C

A heavy boy and a lightweight girl are balanced on a massless seesaw. The boy moves backward, increasing his distance from the pivot point. What happens to the seesaw? a. Nothing; the seesaw will remain balanced. b. It is impossible to predict without knowing additional information. c. The side the boy is sitting on will tilt downward. d. The side the girl is sitting on will tilt downward.

C

A lump of putty and a rubber ball have equal mass. Both are thrown with equal speed against a wall. The putty sticks to the wall. The ball bounces back at nearly the same speed with which it hit the wall. Which object experiences the greater momentum change? a. The putty experiences the greater momentum change. b. Not enough information is given to determine the answer. c. The ball experiences the greater momentum change. d. They both experience the same momentum change.

C

A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of −2.0 m/s. What is the velocity of the two balls after the elastic collision? a. The yellow ball stops immediately, and the red ball has a velocity of −1 m/s. b. The velocity of the red ball is +2.0 m/s; the velocity of the yellow ball is −3.0 m/s. c. The velocity of the red ball is −2.0 m/s; the velocity of the yellow ball is +3.0 m/s. d. The red ball stops immediately, and the yellow ball has a velocity of +1 m/s. e. The velocity of the red ball is −3.0 m/s; the velocity of the yellow ball is +2.0 m/s. f. The velocity of the red ball is +3.0 m/s; the velocity of the yellow ball is −2.0 m/s.

C

A solid sphere and a hollow sphere (spherical shell) of the same mass and same radius rotate with the same amount of kinetic energy. Which one is rotating faster? a. Neither; they must be rotating at the same speed. b. the hollow sphere c. the solid sphere

C

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. a. the object was at rest at the end of this interval b. the object was at rest during this entire interval c. the object's final speed was the same as its initial speed

C

If the net work done on an object is positive, what can you conclude about the object's motion? a. The object is at rest; its position is constant. b. The object is moving with a constant velocity. c. The object is speeding up. d. The object is slowing down.

C

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. Not enough information is given to determine the answer. b. There is a greater impulse of the force on the brick from the gelatin. c. The impulse is the same in both situations. d. There is a greater impulse of the force on the brick from the wall.

C

Rather than ascribing the increased kinetic energy of the stone to the work of gravity, we now (when using potential energy rather than work-energy) say that the increased kinetic energy comes from the ______ of the _______ energy. Choose the best answer to fill in the blanks above: a. work / potential b. force / kinetic c. change / potential

C

To calculate the change in kinetic energy, you must know the force as a function of _______. The work done by the force causes the kinetic energy change. Choose the best answer to fill in the blank above: a. acceleration b. work c. position d. potential energy

C

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. a. different magnitudes, but the same sign b. different magnitudes and opposite signs c. the same magnitude and sign d. the same magnitude, but opposite signs

C

A 1000-kg car is moving around a circular turn with a radius of 18.5 meters and decreasing in speed at a rate of 35.2 m/s2. At the instant the car is moving at 16.8 m/s, what is the car's total acceleration? Atotal=√at^2+ac^2 a. 35.2 m/s^2 b. 15.3 m/s^2 c. 19.9 m/s^2 d. 38.4 m/s^2 e. 50.5 m/s^2

D

A 1000-kg car is moving at a constant speed around a circular turn with a radius of 18.5 meters. How fast must the car move to have an acceleration of 25.2 m/s2? v=√ar a. 34.3 m/s b. 466 m/s c. 1.18 m/s d. 21.6 m/s

D

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? a. The speed of the freight car cannot be determined from the information given. b. The speed of the freight car remains the same. c. The speed of the freight car increases. d. The speed of the freight car decreases.

D

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 greater linear speed? a. Both the girl and the boy have the same nonzero linear speed. b. Both the girl and the boy have zero linear speed. c. The boy has greater linear speed. d. The girl has greater linear speed.

D

If the net work done on an object is zero, what can you determine about the object's kinetic energy? a. The object's kinetic energy is zero. b. The object's kinetic energy is decreasing. c. The object's kinetic energy is increasing. d. The object's kinetic energy remains the same.

D

Max is pushing on the edge (2.4 m from the center) of the merry-go-round to make it rotate. Maya is riding on the merry-go-round, sitting 1.2 m from the center. If Max increases the merry-go-round's angular speed from 0.52 rev/s to 1.5 rev/s in 2.2 s, what is the merry-go-round's angular acceleration? a. 0.45 rad/s^2 b. 25.8 rad/s^2 c. 23.4 rad/s^2 d. 22.8 rad/s^2 e. 26.7 rad/s^2

D

Max is pushing on the edge (2.4 m from the center) of the merry-go-round to make it rotate. Maya is riding on the merry-go-round, sitting 1.2 m from the center. If Max is pushing the merry-go-round at 1.4 m/s, how fast is Maya moving? a. 0.58 m/s b. 2.1 m/s c. 4.0 m/s d. 0.70 m/s e. 1.4 m/s

D

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. What is the net work done on the sled while Max pulls it 5 m across the road? a. 58 J b. 78 J c. 7.6 J d. 38 J e. 16 J

D

Two children are riding on a merry-go-round that is rotating with a constant angular speed. Abbie is one meter from the center of the merry-go-round, whereas Zak is two meters from the center. Abbie's acceleration is ___________ Zak's acceleration. a. a quarter of b. twice c. equal to d. half of e. four times

D

What represents the impulse of the force in a graph of force versus time? a. Impulse cannot be determined from this type of graph. b. The impulse is equal to length of the curve. c. The impulse is equal to the slope of the curve. d. The impulse is equal to the area under the curve. e. The impulse is equal to the product of the maximum force times the maximum time.

D

Which statement must be true for the momentum of a system to be conserved? a. There are no external forces acting on the system. b. The internal forces sum to zero. c. The net external force on the system is non-zero. d. The net external force on the system is zero.

D

You are riding on a roller coaster that starts from rest at a height of 25.0 m and moves down a frictionless track to a height of 3.00 m. How fast are you moving when you arrive at the 3.00-m height?vf=√−2gΔy a. 23.4 m/s b. 14.7 m/s c. 22.1 m/s d. 20.8 m/s

D

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

D,E,F

Max and Maya are riding on a merry-go-round that rotates at a constant speed. If the merry-go-round makes 3.5 revolutions in 9.2 seconds, what is its angular speed? a. 0.0066 rad/s b. 22 rad/s c. 0.38 rad/s d. 5.1 rad/s e. 2.4 rad/s

E

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. If the sled's speed is 1.5 m/s as Max pulls it onto the road, what is the sled's speed after Max pulls it 5 m across the road? a. 2.8 m/s b. 6.0 m/s c. 3.2 m/s d. 2.0 m/s e. 2.5 m/s

E

Person B does twice the work of person A, and in one-half of the time . How does the power output of person B compare to person A? a. Person B has twice the power output of person A. b. Person B has half the power output of person A. c. Person B has the same power output as person A. d. Person B has eight times the power output of person A. e. Person B has four times the power output of person A.

E

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? a. The maximum heights of the two balls are equal. b. The maximum height of the second ball is eight times that of the first ball. c. The maximum height of the second ball is 1.41 times that of the first ball. d. The maximum height of the second ball is two times that of the first ball. e. The maximum height of the second ball is four times that of the first ball.

E

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? a. Object 2 rises to the greater height because it possesses a larger amount of kinetic energy. b. Object 1 rises to the greater height because it possesses a smaller amount of kinetic energy. c. Object 1 rises to the greater height because it weighs less. d. Object 2 rises to the greater height because it contains more mass. e. The two objects rise to the same height.

E

When a person steps forward out of a small boat onto a dock, the boat recoils backward in the water. Why does this occur? a. The total mechanical energy of the system is conserved. b. The energy of the person is greater than the energy of the boat. c. The momentum of the person is greater than the momentum of the boat. d. The momentum of the boat is greater than the momentum of the person. e. The total momentum of the system is conserved. f. The energy of the boat is greater than the energy of the person.

E

A girl moves quickly to the center of a spinning merry-go-round, traveling along the radius of the merry-go-round. Which of the following statements are true? Check all that apply. a. The angular speed of the system remains constant. b. The angular speed of the system decreases. c. The moment of inertia of the system remains constant. d. The moment of inertia of the system increases. e. The angular speed of the system increases. f. The moment of inertia of the system decreases.

E,F

Which of the following statements is/are true? Check all that apply. a. The SI unit of power is the watt. b. Power is the rate at which energy is transformed. c. Power is the rate at which work is done. d. The SI unit of power is the horsepower. e. A person is limited in the total work he or she can do by their power output.

A,B,C

Which of the following statements are true? Select all correct responses. Choose all that apply. a. The vector sum of forces acting on a particle equals the rate of change of momentum of the particle with respect to time. b. The total momentum of an isolated system is constant. c. The total momentum of any system is constant. d. The total momentum of any number of particles is equal to the vector sum of the momenta of the individual particles. e. The vector sum of forces acting on a particle equals the rate of change of velocity of the particle with respect to time. f. The total momentum of any number of particles is equal to the algebraic sum of the momenta of the individual particles.

A,B,D

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? Check all that apply. a. The angular velocity depends upon the height of the incline. b. The angular velocity depends upon the length of the incline. c. The angular velocity depends upon the radius of the sphere. d. The angular velocity depends upon the mass of the sphere.

A,C

When a constant force acts on an object, what does the object's change in momentum depend upon? Check all that apply. a. The change in momentum depends upon the mass of the object. b. The change in momentum depends upon the change in the position of the object. c. The change in momentum depends upon the time interval during which the force acts. d. The change in momentum depends upon the change in the velocity of the object. e. The change in momentum depends upon the magnitude of the force.

A,C,D,E

For an elastic collision, which of the following statements are true? Choose all that apply. a. Momentum is conserved. b. Momentum is lost. c. Momentum is gained. d. Kinetic energy is conserved. e. Kinetic energy is gained. f. Kinetic energy is lost.

A,D

For an INELASTIC collision, which of the following statements are true? Choose all that apply. a. Momentum is conserved. b. Momentum is gained. c. Kinetic energy is gained. d. Momentum is lost. e. Kinetic energy is lost. f. Kinetic energy is conserved.

A,E

A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____. a. zero b. negative c. positive

B

A person applies a horizontal 50 NN force on a crate, causing it to move horizontally at a constant speed through a distance of 10 mm. What is the net work done on the crate? a. The net work done on the crate is 0.2 J. b. The net work done on the crate is 500 J. c. The net work done on the crate is 250 J. d. The net work done on the crate is zero joules. e. The net work done on the crate is 5 J.

B

An object weighing 20 N moves horizontally toward the right a distance of 5.0 m. What is the work done on the object by the force of gravity? a. The work done on the object by the force of gravity is 0.25 J. b. The work done on the object by the force of gravity is zero joules. c. The work done on the object by the force of gravity is 4.0 J. d. The work done on the object by the force of gravity is 50 J. e. The work done on the object by the force of gravity is 100 J.

B

Earth is 149.6 billion meters from the Sun and takes 365 days to make one complete revolution around the Sun. Mars is 227.9 billion meters from the Sun and has an orbital period of 687 days. What is the ratio of Earth's centripetal acceleration to Mars's centripetal acceleration? a. 1.88 b. 2.33 c. 0.430 d. 0.809 e. 1.24

B

The work-energy theorem states that a force acting on a particle as it moves over a ______ changes the ______ energy of the particle if the force has a component parallel to the motion. Choose the best answer to fill in the blanks above: a. distance / potential b. distance / kinetic c. vertical displacement / potential d. none of the above

B

Two equal forces are applied perpendicular to a door. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Which force exerts the greater torque? a. Both forces exert zero torques. b. The force applied at the doorknob exerts the greater torque. c. The force applied at the midpoint of the door exerts the greater torque. d. Both forces exert equal nonzero torques.

B

Two racecars are driving at constant speeds around a circular track. Both cars are the same distance away from the center of the track, but car 2 is driving twice as fast as car 1. The acceleration of car 2 is ___________ the acceleration of car 1. a. half of b. four times c. twice d. a quarter of e .equal to

B

While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. Her friend, a hockey player, then shoots a hockey puck at each shoe. The first puck immediately comes to rest after it collides with the left shoe. The second puck rebounds after it collides with the right shoe. If each hockey puck has the same incoming speed, which shoe has greater speed after the collision? a. The left shoe b. The right shoe c. Both shoes have the same speed.

B

A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward? a. Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward. b. Work done by gravity is negative while the ball is traveling both upward and downward. c. Work done by gravity is positive while the ball is traveling both upward and downward. d. Work done by gravity is positive while the ball is traveling upward and negative while the ball is traveling downward.

A

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 greater tangential acceleration. a. Both the girl and the boy have zero tangential acceleration. b. Both the girl and the boy have the same nonzero tangential acceleration. c. The boy has greater tangential acceleration. d. The girl has greater tangential acceleration.

A

If the larger wheel in (Figure 1) turns clockwise, is the angular velocity of the smaller wheel positive or negative using the convention described in the video? a. positive b. negative

A

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. When Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground, how much work does Max do on the sled as he pulls his sister 25 m in the snow? a. 290 J b. 11.6 J c. 77.6 J d. 300 J

A

This process happens in such a way that total mechanical energy, equal to the ______ of the kinetic and potential energies, is _______. Choose the best answer to fill in the blanks above: a. sum / conserved b. sum / zero c. sum / not conserved d. difference / conserved

A

To illustrate the work-energy concept, consider the case of a stone falling from Xinitial to Xfinal under the influence of gravity. Using the work-energy concept, we say that work is done by the gravitational _____, resulting in an increase of the ______ energy of the stone. Choose the best answer to fill in the blanks above: a. force / kinetic b. potential energy / potential c. force / potential d. potential energy / kinetic

A