1. Q7.1
As a piece of fruit falls,
1. the gravitational force does positive work on it and the gravitational potential energy increases
2. the gravitational force does positive work on it and the gravitational potential energy decreases
3. the gravitational force does negative work on it and the gravitational potential energy increases
4. the gravitational force does negative work on it and the gravitational potential energy decreases

2. A7.1
As a piece of fruit falls,
1. the gravitational force does positive work on it and the gravitational potential energy increases
2. the gravitational force does positive work on it and the gravitational potential energy decreases
3. the gravitational force does negative work on it and the gravitational potential energy increases
4. the gravitational force does negative work on it and the gravitational potential energy decreases

3. Q7.2
You toss a kg baseball straight upward so that it leaves your hand moving at 20.0 m/s. The ball reaches a maximum height y2.
What is the speed of the ball when it is at a height of y2/2? Ignore air resistance.
m/s
2. less than 10.0 m/s but more than zero
3. more than 10.0 m/s
4. not enough information given to decide

4. A7.2
You toss a kg baseball straight upward so that it leaves your hand moving at 20.0 m/s. The ball reaches a maximum height y2.
What is the speed of the ball when it is at a height of y2/2? Ignore air resistance.
m/s
2. less than 10.0 m/s but more than zero
3. more than 10.0 m/s
4. not enough information given to decide

5. Q7.3
As this skateboarder travels along a curved, frictionless track, mechanical energy is conserved. Why?
(Ignore air resistance.)
1. The track is circular.
2. The normal force is balanced by centrifugal force.
3. The normal force is balanced by centripetal force.
4. The normal force acts perpendicular to the track.
5. The skateboarder’s acceleration is perpendicular to the track.

6. A7.3
As this skateboarder travels along a curved, frictionless track, mechanical energy is conserved. Why?
(Ignore air resistance.)
1. The track is circular.
2. The normal force is balanced by centrifugal force.
3. The normal force is balanced by centripetal force.
4. The normal force acts perpendicular to the track.
5. The skateboarder’s acceleration is perpendicular to the track.

7. Q7.4
The two ramps shown are both frictionless, and the heights y1 and y2 are the same for each ramp.If a block of mass m is released from rest at the left-hand end of each ramp, which block arrives at the right-hand end with the greater speed?
1. The block on the curved track.
2. The block on the straight track.
3. Both blocks arrive at the right-hand end with the same speed.
4. The answer depends on the shape of the curved track.

8. A7.4
The two ramps shown are both frictionless, and the heights y1 and y2 are the same for each ramp.If a block of mass m is released from rest at the left-hand end of each ramp, which block arrives at the right-hand end with the greater speed?
1. The block on the curved track.
2. The block on the straight track.
3. Both blocks arrive at the right-hand end with the same speed.
4. The answer depends on the shape of the curved track.

9. Q7.5
The graph shows the potential energy U for a particle that moves along the x-axis.
The particle is initially at x = x4 and moving in the negative x-direction. At which of the labeled points does the particle have the greatest speed?
1. at x = x1
2. at x = x2
3. at x = x3
4. at x = x4
5. more than one of the above

10. A7.5
The graph shows the potential energy U for a particle that moves along the x-axis.
The particle is initially at x = x4 and moving in the negative x-direction. At which of the labeled points does the particle have the greatest speed?
1. at x = x1
2. at x = x2
3. at x = x3
4. at x = x4
5. more than one of the above

11. Q7.6
The graph shows the potential energy U for a particle that moves along the x-axis.
At which of the labeled values of x is there zero force on the particle?
1. at both x = x1 and x = x3
2. at x = x2 only
3. at x = x4 only
4. at both x = x2 and x = x4

12. A7.6
The graph shows the potential energy U for a particle that moves along the x-axis.
At which of the labeled values of x is there zero force on the particle?
1. at both x = x1 and x = x3
2. at x = x2 only
3. at x = x4 only
4. at both x = x2 and x = x4

13. Q7.7
The graph shows the force Fx that acts on a particle as it moves along the x-axis.
At which of the labeled values of x is the potential energy a maximum?
1. at x = x1 and x = x5
2. at x = x4
3. at x = x2 and x = x6
4. at x = x3 and x = x7
5. more than one of the above

14. A7.7
The graph shows the force Fx that acts on a particle as it moves along the x-axis.
At which of the labeled values of x is the potential energy a maximum?
1. at x = x1 and x = x5
2. at x = x4
3. at x = x2 and x = x6
4. at x = x3 and x = x7
5. more than one of the above