A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A: Thrown straight up. Case B: Thrown straight down. Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below?

A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A: Thrown straight up. Case B: Thrown straight down. Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below?
17. Joe and Bill throw identical balls vertically upward. Joe throws his ball with an initial speed twice as high as Bill. The maximum height of Joe’s ball will be
18. A tennis ball bounces on the floor three times. If each time it loses 23% of its energy due to heating, how high does it bounce after the third time, provided we released it 1.1 m from the floor?
19. In the absence of friction, how much work would a child do while pulling a 12 kg wagon a distance of 4.2 m with a 22 N force?
20. An engine is being used to raise a 89 kg crate vertically upward. If the power output of the engine is 1620 W, how long does it take the engine to lift the crate a vertical distance of 18.7 m? Friction in the system is negligible.
21. You carry a 7.0 kg bag of groceries 1.2 m above the ground at constant velocity across a 6.9 m room. How much work do you do on the bag in the process?
22. A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 8.8 m above the ground. What is the mass of the box?
23. Two balls having different masses reach the same height when shot into the air from the ground.
If there is no air drag, which of the following statements must be true? (More than one statement may be true.)
24. A 1000.0 kg car experiences a net force of 9500 N while decelerating from 30.0 m/s to 17.0 m/s. How far does it travel while slowing down?
25. A sand mover at a quarry lifts 2,000 kg of sand per minute a vertical distance of 12 meters. The sand is initially at rest and is discharged at the top of the sand mover with speed 5 m/s into a loading chute. At what minimum rate must power be supplied to this machine?
26. A brick is dropped from the top of a building through the air (friction is present) to the ground below.
How does the brick’s kinetic energy (K) just before striking the ground compare with the gravitational potential energy (Ugrav) at the top of the building? Set y=0at the ground level.
27. A person stands on the edge of a cliff. She throws three identical rocks with the same speed. Rock X is thrown vertically upward, rock Y is thrown horizontally, and rock Z is thrown vertically downward. Assuming the elevation loss of the three rocks is the same (the base of the cliff is flat), which rock hits the ground with the highest speed?
28. You slam on the brakes of your car in a panic and skid a distance d on a straight and level road.
If you had been traveling twice as fast, what distance would the car have skidded under the same conditions?
29. Spring #1 has a force constant of k, and spring #2 has a force constant of 2k. Both springs are attached to the ceiling, identical weights are hooked to their ends, and the weights are allowed to stretch the springs.
The ratio of the energy stored by spring #1 to that stored by spring #2 is
30. Consider two frictionless inclined planes with the same vertical height. Plane 1 makes an angle of 25.0∘ with the horizontal, and plane 2 makes an angle of 60.0∘ with the horizontal. Mass m1 is placed at the top of plane 1, and mass m2 is placed at the top of plane 2. Both masses are released at the same time.
At the bottom, which mass is going faster?