103. The graph below represents the kinetic energy, gravitational potential energy, and total mechanical energy of a moving block. internal Energy vs. Distance Moved Key Kinetic energy Energy I force Force is Gravitational potential energy Total mechanical energy Distance moved Which best describes the motion of the block? (1) accelerating on a flat horizontal surface (2) sliding up a frictionless incline (3) falling freely (4) being lifted at constant velocity - at ong 104. An object is thrown vertically upward. Which pair of graphs best represents the object's kinetic energy and gravitational potential energy as functions of its displacement while it rises? Displacement Disela Kinetic Energy Potential Energy inetic Energy tential Energy

103. The graph below represents the kinetic energy, gravitational potential energy, and total mechanical energy of a moving block. internal Energy vs. Distance Moved Key Kinetic energy Energy I force Force is Gravitational potential energy Total mechanical energy Distance moved Which best describes the motion of the block? (1) accelerating on a flat horizontal surface (2) sliding up a frictionless incline (3) falling freely (4) being lifted at constant velocity - at ong 104. An object is thrown vertically upward. Which pair of graphs best represents the object's kinetic energy and gravitational potential energy as functions of its displacement while it rises? Displacement Disela Kinetic Energy Potential Energy inetic Energy tential Energy

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter7: Work, Energy, And Energy Resources

Section: Chapter Questions

Problem 21PE: In a downhill ski race, surprisingly, little advantage is gained by getting a running start. (This...

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A roller-coaster car of mass 1.50 103 kg is initially at the top of a rise at point . It then moves 35.0 m at an angle of 50.0 below the horizontal to a lower point . (a) Find both the potential energy of the system when the car is at points and and the change in potential energy as the car moves from point to point , assuming y = 0 at point . (b) Repeat part (a), this time choosing y = 0 at point , which is another 15.0 m down the same slope from point .
Consider the following scenario. A car for which friction is not negligible accelerates from rest down a hill, running out of gasoline after a short distance. The driver lets the car coast farther down the hill, then up and over a small crest. He then coasts down that hill into a gas station, where he brakes to a stop and fills the tank with gasoline. Identify the forms of energy the car has, and how they are changed and transferred in this series of events. (See Figure 7.34.) Figure 7.34 A car experiencing non-negligible friction coasts down a hill, over a small crest then dill again, and comes to a stop at a gas station.
Ignoring details associated with friction, extra forces exerted by arm and leg muscles, and other factors, we can consider a pole vault as the conversion of an athlete’s running kinetic energy to gravitational potential energy. If an athlete is to lift his body 4.8 m during a vault, what speed must he have when he plants his pole?
What does work on a shuffleboard puck as it slides to rest? Why is the board dusted, and how does this affect work?
A roller-coaster car of mass 1.50 103 kg is initially at the top of a rise at point . It then moves 35.0 m at an angle of 50.0 below the horizontal to a lower point . (a) Find both the potential energy of the system when the car is at points and and the change in potential energy as the car moves from point to point , assuming y = 0 at point . (b) Repeat part (a), this time choosing y = 0 at point , which is another 15.0 m down the same slope from point .
Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 2.0 gal of gasoline. Only 30% of the gasoline goes into useful work by the force that keeps the car moving at constant speed despite friction. (See Table 7.1 for the energy content of gasoline.) (a) What is the magnitude of the force exerted to keep the car moving at constant speed? (b) If the required force is directly proportional to speed, how many gallons will be used to drive 108 km at a speed of 28.0 m/s?
The person in Figure 7.33 does work on the lawn mower. Under what conditions would the mower gain energy? Under what conditions would it lose energy?
A student has the idea that the total work done on an object is equal to its final kinetic energy. Is this idea true always, sometimes, or never? Ii it is sometimes true, under what circumstances? If it is always or never true, explain why.
. The fastest that a human has run is about 12 m/s. (a) If a pole vaulter could run this fast and convert all of her kinetic energy into gravitational potential energy, how high would she go? (b) Compare this height with the world record in the pole vault.
If you run down some stairs and stop, what happens to your kinetic energy and your initial gravitational potential energy?
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In a downhill ski race, surprisingly, little advantage is gained by getting a running start. (This is because the initial kinetic energy is small compared with the gain in gravitational potential energy on even small hills.) To demonstrate this, find the final speed and the time taken for a skier who skies 70.0 m along a 30° slope neglecting friction: (a) Starting from rest. (b) Starting with an initial speed of 2.50 m/s. (c) Does the answer surprise you? Discuss why it is still advantageous to get a running start in very competitive events.