# Physics Principles and Problems 2009

## Chapter 11: Energy and Its Conservation

### Chapter Test Practice

 1 The __________ is the position at which gravitational potential energy is zero. Need a Hint? A) release point B) height C) reference level D) initial position 2 Stored energy that is a result of the gravitational interaction between an object and Earth is __________. Need a Hint? A) the reference level B) gravitational potential energy C) elastic potential energy D) mechanical energy 3 You lift a 2.73-kg textbook from the floor to a shelf 1.75 m above the floor. What is the book's gravitational potential energy relative to the floor? Need a Hint? A) 14.3 J B) 46.8 J C) 93.1 J D) -46.8 J 4 A 75-kg rock climber first climbs 25 m to the top of a quarry, then descends 75 m from the top to the bottom of the quarry. If the initial height is the reference level, what is the potential energy at the bottom? Need a Hint? A) -3.7×104 J B) 1.8×104 J C) -5.5×104 J D) 3.7×104 J 5 Objects that are lifted against the force of gravity have stored energy known as __________. Need a Hint? A) reference levels B) kinetic energy C) resistance D) potential energy 6 A 75-kg rock climber first climbs 25 m to the top of a quarry, then descends 75 m from the top to the bottom of the quarry. If the initial height is the reference level, what is the potential energy of the system (climber plus Earth) at the top? Need a Hint? A) 3.7×104 J B) 1.8×104 J C) -1.8×104 J D) -3.7×104 J 7 The equation that represents gravitational potential energy is __________. Need a Hint? A) PEg = Fd B) PEg = 1/2mv2 C) PEg = mgh D) PEg = E + KE 8 In an accident on a slippery road, a car with mass 800.0 kg, moving at 12.0 m/s, smashes into the rear end of a car with mass 1250 kg moving at 8.0 m/s in the same direction. How much kinetic energy was lost in the collision if the wrecked cars lock together? Need a Hint? A) 3.9×103 J B) 3.9×104 J C) 6.1×104 J D) 4.1×104 J 9 In the figure below, case 3, if vi were doubled, how would the magnitude of the final velocity be affected? (20.0K) Need a Hint? A) It wouldn't change. B) It would be halved. C) It would be quadrupled. D) It would be doubled. 10 If the mass of the ball rolling down the ramp in Figure 11-10 were doubled, how would its speed at the bottom of the ramp be affected? Need a Hint? A) It wouldn't change. B) It would be doubled. C) It would be quadrupled. D) It would be halved. 11 In the figure below, if cart D were given an initial velocity of 1 m/s to the left, what would the final velocities of each cart be? (12.0K) Need a Hint? A) cart C, 2 m/s to the left; cart D, 1 m/s to the left B) cart C, 0 m/s; cart D, 0 m/s C) cart C, 1 m/s to the left; cart D, 1 m/s to the right D) cart C, 0 m/s; cart D, 2 m/s to the right 12 A 4.5-kg rock loses 375 J of potential energy while falling to the ground. What is the rock's speed just before it strikes the ground? Need a Hint? A) 9.1 m/s B) 13 m/s C) 20 m/s D) 18 m/s 13 A bike rider approaches a hill at a speed of 3.5 m/s. The mass of the bike and rider together is 77 kg. The rider coasts up the hill. Assuming that there is no friction, at what height will the bike come to rest? Need a Hint? A) 1.6 m B) 4.1 m C) 3.7 m D) 0.62 m 14 A large chunk of ice with mass 12.0 kg falls from a roof 6.00 m above the ground. Ignoring air resistance, what is the speed of the ice when it reaches the ground? Need a Hint? A) 12.5 m/s B) 12.1 m/s C) 10.8 m/s D) 7.67 m/s 15 A large chunk of ice with mass 12.0 kg falls from a roof 6.00 m above the ground. Ignoring air resistance, what is the kinetic energy of the ice when it reaches the ground? Need a Hint? A) 7.06×102 J B) -7.06×103 J C) -7.06×102 J D) 7.06×103 J 16 A collision in which kinetic energy decreases is called a(n) __________. Need a Hint? A) inelastic collision B) energy conservation C) elastic collision D) mechanical collision 17 The sum of the kinetic and gravitational potential energies of a system is called __________. Need a Hint? A) reference energy B) conserved energy C) momentum D) mechanical energy 18 If no other forms of energy besides kinetic and gravitational potential energy are present, then mechanical energy is represented by the equation __________. Need a Hint? A) PEg = E + KE B) ME = 1/2 (KE)(PEg)2 C) PEg = mgh D) E = KE + PEg 19 A bike rider approaches a hill at a speed of 3.5 m/s. The mass of the bike and rider together is 77 kg. What is the initial kinetic energy of the system? Need a Hint? A) 1.2×103 J B) 3.1×103 J C) 4.7×102 J D) 2.6×103 J 20 The law of conservation of energy states that __________. Need a Hint? A) in a closed, isolated system, the total amount of energy is constant B) the total amount of energy in any system is the sum of its kinetic and gravitational potential energies C) if a system is isolated from external forces, then the total amount of energy is constant D) the total amount of energy in any system is its mechanical energy