Download Ch. 8 Conceptual and Mathematical Questions

Ch. 8 Conceptual and Mathematical Questions
Vocabulary
Joule, Energy, KE, Potential Energy, Gravitational Potential Energy, Elastic Potential
Energy, Conservative Force, Non-Conservative Force, Non-Conservative Work,
Mechanical Energy, Law of Conservation of Energy
Matching
A) Energy
C) Kinetic Energy
E) Potential Energy
B) Joule
D) Law of Conservation of Energy
1.___________ The SI unit of work and energy is the _____.
2.___________ Energy that is stored in an object by virtue of its position is _____.
3.___________ Within a closed, isolated system, energy can change form, but the total amount
of energy is constant.
4.___________ The form of energy found in moving objects is _____.
5.___________ The ability of an object to produce a change in itself or its surroundings is _____.
Multiple Choice
6. Which of these is not needed to find the kinetic energy of an object?
A) Shape
B) Mass
C) Velocity
D) None of these
7. When you throw a ball up into the air, the total energy of the ball at any point in its flight
can be expressed by the kinetic energy _______ the potential energy.
A) times
B) minus
C) divided by
D) plus
8. As an object falls towards Earth, the potential energy of the object
A) increases
B) decreases
C) remains the same.
9. The total amount of energy in an isolated, closed system
A) is increasing
B) is decreasing
C) remains constant
D) cannot be measured
10. The gravitational potential energy of an object close to Earth is directly related to
A) its mass
LPPACS – Schmidt
B) its height above Earth
C) its velocity
D) both a and b
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Ch. 8 Conceptual and Mathematical Questions
Short Answer
11. Can the kinetic energy of an object be negative? Explain.
12. Can the gravitational potential energy of an object be negative? Explain
13. Two water slides at a pool are shaped differently, but
start at the same height h. Two riders, Paul and
Kathleen, start from rest at the same time on different
slides. (Ignore friction and assume both slides have
the same path length.)
(a) Which rider, Paul or Kathleen, is traveling
faster at the bottom?
(b) Which rider makes it to the bottom first?
14. Is it possible for a system to have negative potential energy? Talk about both types.
15. A lemming walks off of a cliff. Describe what happens to the potential and kinetic
energy of the rodent as it falls and then hits the ground.
16. Car J moves twice as fast as car K, and car J has a fourth of the mass of car K. What is the
ratio of the kinetic energy of car J to that of car K?
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Ch. 8 Conceptual and Mathematical Questions
Math Problems
17. A 1000 kg car is traveling at a constant speed of 30 m/s. How much energy is dissipated
as the car comes to rest?
18. A 70-kg stuntman is attached to a bungee cord with an un-stretched length of 15 m. He
jumps off a bridge and comes to a stop just above the river, giving the bungee cord a
stretched length of 44 m. What is the spring constant of the bungee cord?
19. A 25-kg box is held 1.5 m above the floor.
a. What type of energy does it have?
b. Calculate how much energy it has.
20. A 500-kg motorcycle traveling at a speed of 17.5 m/s.
a. What type of energy does it store?
b. Calculate how much energy it has.
c. How much energy will it have if it travels at twice the speed?
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Ch. 8 Conceptual and Mathematical Questions
21. How much elastic energy does a bow need to store to shoot a 50-gram arrow at (a) 25
m/s and (b) twice the previous speed, 50 m/s?
22. A cart starts from rest at the top of a hill, and is
bumped down the rough hill.
a. Calculate the initial amount of energy
stored in the cart.
b. Determine final velocity of the cart at the bottom, if 100 J of the energy is
dissipated by friction.
23. A spring whose spring constant is 850 N/m is compressed 0.40 m.
a. What is the maximum speed it can give to a 500 g ball?
b. If the ball travels up an incline and 34 J of work is done by friction, how high can
it rise?
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Ch. 8 Conceptual and Mathematical Questions
24. A 24 kg child descends a 5.0 m high slide and reaches the ground with a speed of 2.8
m/s. How much energy was dissipated due to friction in the process?
25. Suppose a robust 40 kg Wile E. Coyote was shot straight up with an initial velocity of 50
m/s.
a. Assuming no energy is dissipated, what is the maximum height he could reach?
b. What would be the maximum height reached if 40 N of friction due to air resistance
acts?
26. A 6.0 kg cat is napping on the top of a refrigerator when he rolls over and falls. He has
86 J of kinetic energy just before he lands on his feet on the floor. How tall is the
refrigerator?
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