# Chapter Test : Work, Energy And Power

Questions pertain to the analysis of motion using relationships related to work and energy, mainly energy conservation and work-energy transfer principles. The following concepts are emphasized: work, positive work, negative work, energy, power, conservative (internal) forces, non-conservative (external) forces, potential energy, kinetic energy, mechanical energy, conservation of energy, work-energy theorem, pendulum, and incline planes.

Changes are done, please start the quiz.

 1 An arrow is drawn back so that 50 Joules of potential energy is stored in the stretched bow and string. Whenreleased, the arrow will have a kinetic energy of ____ Joules. Presume that the value of g is ~10 m/s/s.
 A. 50
 B. More than 50
 C. Less than 50
 D. None of the above.
 2 Which of the following statements are true about potential energy?
 A. Moving objects cannot have potential energy.
 B. Both gravitational and elastic potential energy are dependent upon the mass of an object.
 C. Potential energy is the energy stored in an object due to its position.
 D. None of the above.
 3 Which requires more work: lifting a 50.0 kg crate a vertical distance of 2.0 meters or lifting a 25.0 kg crate a vertical distance of 4.0 meters? Presume that the value of g is ~10 m/s/s.
 A. Lifting the 50 kg crate
 B. Both require the same amount of work
 C. Lifting the 25 kg crate
 D. None of the above.
 4 A 1 kg ball is dropped from the top of a cliff and falls with a constant acceleration due to gravity (9.8 m/s2). Assume that effects of air resistance can be ignored. How fast is the ball going after it has fallen by 10 m?
 A. 45 m/s
 B. 14 m/s
 C. 87 m/s
 D. None of the above.
 5 A 10-Newton object moves to the left at 1 m/s. Its kinetic energy is approximately ____ Joules. Presume that the value of g is ~10 m/s/s.
 A. More than 10
 B. 0.5
 C. 10
 D. None of the above.
 6 A car having a mass of 500 kg is initially at rest. A constant 1,000 N net force acts on the car over a distance of 50 m, causing the car to speed up. After it travels 50 m, the car moves with constant velocity. What is the net force on the car while its moving with constant velocity? d.) What is the total work done on the car while its moving with constant velocity?
 A. Faster moving objects would have more kinetic energy than other objects of the same mass. However, another object could have less speed and make up for this lack of speed in terms of a greater mass.
 B. When the car moves with constant velocity, its acceleration is zero. By Newton's second law, this means that the net force is zero.
 C. More massive objects would have more kinetic energy than other objects with the same speed. However, another object could have less mass and make up for this lack of mass in terms of a greater speed.
 D. None of the above.
 7 Which of the following statements are true about conservative and non-conservative forces?
 A. Physicists envy biologists' ability to instill order on the world of animal species through their taxonomic system. So physicists have made a habit of identifying forces as conservative and non-conservative forces in order to instill order on the world of forces.
 B. A force is regarded as a non-conservative force if it does not add mechanical energy to a system of objects.
 C. The force of gravity and elastic (spring) force are both examples of a conservative forces.
 D. None of the above.
 8 A 62.9-kg downhill skier is moving with a speed of 12.9 m/s as he starts his descent from a level plateau at 123-m height to the ground below. The slope has an angle of 14.1 degrees and a coefficient of friction of 0.121. The skier coasts the entire descent without using his poles; upon reaching the bottom he continues to coast to a stop; the coefficient of friction along the level surface is 0.623. How far will he coast along the level area at the bottom of the slope?
 A. 629 m
 B. 121 m
 C. 116 m
 D. None of the above.
 9 Which of the following statements are true about mechanical energy?
 A. The total amount of mechanical energy of an object is the sum of its potential energy and the kinetic energy.
 B. Heat is a form of mechanical energy.
 C. The mechanical energy of an object is always conserved.
 D. None of the above.
 10 Luke Autbeloe stands on the edge of a roof throws a ball downward. It strikes the ground with 100 J of kinetic energy. Luke now throws another identical ball upward with the same initial speed, and this too falls to the ground. Neglecting air resistance, the second ball hits the ground with a kinetic energy of ____ J. Presume that the value of g is ~10 m/s/s.
 A. Less than 100
 B. 100
 C. More than 200
 D. None of the above.
 11 A car having a mass of 500 kg is initially traveling with a speed of 80 km/hr. It slows down at a constant rate, coming to a stop in a distance of 50 m. What is the change in the car's kinetic energy over the 50 m distance it travels while coming to a stop?
 A. 1.2x10^5 J
 B. -1.2x10^5 J
 C. -11.2x10^5 J
 D. None of the above.
 12 Approximate the work required lift a 2.5-kg object to a height of 6.0 meters.
 A. ~150 J
 B. ~250 J
 C. ~50 J
 D. None of the above.
 13 A child lifts a box up from the floor. The child then carries the box with constant speed to the other side of the room and puts the box down. How much work does he do on the box while walking across the floor at constant speed? Presume that the value of g is ~10 m/s/s.
 A. Zero J
 B. More than zero J
 D. None of the above.
 14 Which of the following statements are true about kinetic energy?
 A. If an object is on the ground, then it does not have any kinetic energy.
 B. If an object is at rest, then it does not have any kinetic energy.
 C. Kinetic energy is the form of mechanical energy which depends upon the position of an object.
 D. None of the above.
 15 Suzie Lovtaski has a mass of 49.7 kg. She is at rest on top of a hill with a height of 92.6 m and an incline angle of 19.2 degrees. She coasts down the hill to the bottom and eventually comes to a stop; she never uses her poles to apply a force. The coefficient of friction is 0.0873 along the hill and 0.527 along the horizontal surface at the bottom. What total distance will Suzie coast (include both incline and level surface)?
 A. 132 m
 B. 492 m
 C. 332 m
 D. None of the above.
 16 Eddy, whose mass is 65.0-kg, climbs up the 1.60-meter high stairs in 1.20 s. Approximate Eddy's power rating.
 A. P = 849 Watts
 B. P = 749 Watts
 C. P = 659 Watts
 D. None of the above.
 17 A platform diver weighs 500 N. She steps off a diving board that is elevated to a height of 10 meters above the water. The diver will possess ___ Joules of kinetic energy when she hits the water. Presume that the value of g is ~10 m/s/s.
 A. 5000
 B. 500
 C. 10
 D. None of the above.
 18 A car having a mass of 500 kg is initially at rest. A constant 1,000 N net force acts on the car over a distance of 50 m, causing the car to speed up. After it travels 50 m, the car moves with constant velocity. How fast is the car moving after 50 m?
 A. 24 m/s
 B. 14 m/s
 C. 34 m/s
 D. None of the above.
 19 Claire deAisles has just completed her shopping at the grocery food store. She accidentally bumps her 42.5-kg cart, setting it in motion from rest down a hill inclined at 14.9 degrees. Upon descending a distance of 9.27 meters along the inclined plane, the cart hits a tree stump (which was placed in the parking lot for the sole purpose of this problem). A 0.295-kg can of tomato soup is immediately hurled from the moving cart and heads towards Will N. Tasue's brand new Lexus. Upon striking the Lexus, the tomato soup can creates a dent with a depth of 3.16 cm. Noah Formula, who is watching the entire incident and fixing to do some physics, attempts to calculate the average force which the Lexus applies to the soup can. Assume negligible air resistance and friction forces and help Noah out.
 A. 927 N
 B. 149 N
 C. 218 N
 D. None of the above.
 20 A 1000-kg car is moving at 40.0 km/hr when the driver slams on the brakes and skids to a stop (with locked brakes) over a distance of 20.0 meters. How far will the car skid with locked brakes if it is traveling at 120. km/hr? Presume that the value of g is ~10 m/s/s.
 A. 20.0 m
 B. 60.0 m
 C. 180. m
 D. None of the above.
 21 A 29.1-kg sledder is traveling along a level area with a speed of 8.96 m/s when she approaches a gentle incline which makes an angle of 12.5 degrees with the horizontal. If the coefficient of friction between the sled and the incline is 0.109, then what will be her speed at the bottom of the inclined plane, located 8.21 m above the top of the incline.
 A. 12.7 m/s
 B. 291 m/s
 C. 100 m/s
 D. None of the above.
 22 A 1 kg ball is dropped from the top of a cliff and falls with a constant acceleration due to gravity (9.8 m/s2). Assume that effects of air resistance can be ignored.  By how much has the ball's gravitational potential energy changed after it has fallen by 10 m?
 A. -98 J
 B. 98 J
 C. 120 J
 D. None of the above.
 23 Use the work-energy theorem to determine the force required to stop a 988-kg car moving at a speed of 21.2 m/s if there is a distance of 45.7 m in which to stop it.
 A. F = 14.86*103 N
 B. F = 4.86*103 N
 C. F = 5.60*103 N
 D. None of the above.
 24 Calculate the kinetic energy (KE) of a 1500-kg automobile with a speed of 30 m/s.
 A. 12.8 x 10 ^ 5 J
 B. 6.8 x 10 ^ 5 J
 C. 9.8 x 10 ^ 5 J
 D. None of the above.
 25 A 1 kg ball is dropped from the top of a cliff and falls with a constant acceleration due to gravity (9.8 m/s2). Assume that effects of air resistance can be ignored. Is the work done on the ball recoverable?
 A. An object can never have a negative kinetic energy.
 B. Technically no, the work done is not increasing the potential energy, it is decreasing it! We haven't converted energy into a form that we can tap into again.
 C. An object has a kinetic energy of 40 J. If its mass were twice as much, then its kinetic energy would be 80 J.
 D. None of the above.
 26 A 50.0 kg crate is lifted to a height of 2.0 meters in the same time as a 25.0 kg crate is lifted to a height of 4 meters. The rate at which energy is used (i.e., power) in raising the 50.0 kg crate is ____ as the rate at which energy is used to lift the 25.0 kg crate. Presume that the value of g is ~10 m/s/s.
 A. Twice as much
 B. Half as much
 C. The same
 D. None of the above.
 27 A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of ____, but different amounts of ____. Pick the two words which fill in the blanks in their respective order. Presume that the value of g is ~10 m/s/s.
 A. Work, power
 B. Force, work
 C. Energy, work
 D. None of the above.
 28 Using 1000. J of work, a small object is lifted from the ground floor to the third floor of a tall building in 20.0 seconds. What power was required in this task?  Presume that the value of g is ~10 m/s/s.
 A. 20 W
 B. 100 W
 C. 50 W
 D. None of the above.
 29 A ball is projected into the air with 100 J of kinetic energy. The kinetic energy is transformed into gravitational potential energy on the path towards the peak of its trajectory. When the ball returns to its original height, its kinetic energy is ____ Joules. Do consider the effects of air resistance. Presume that the value of g is ~10 m/s/s.
 A. None of the above.
 B. Less than 100
 C. Not enough information given
 D. More than 100
 30 A car having a mass of 500 kg is initially at rest. A constant 1,000 N net force acts on the car over a distance of 50 m, causing the car to speed up. After it travels 50 m, the car moves with constant velocity. What is the total work done on the car while its moving with constant velocity?
 A. The total work is the work done by the net force. After 50 m, the car moves with constant velocity so the net force is zero. This means that the total work done on the car after 50 m is zero. Another way to see this is that the car's speed, hence its KE, isn't changing. This means the total work is zero.
 B. If an object is on the ground, then it does not have potential energy (relative to the ground).
 C. More massive objects would have more kinetic energy than other objects with the same speed. However, another object could have less mass and make up for this lack of mass in terms of a greater speed.
 D. None of the above.
 31 A car having a mass of 500 kg is initially at rest. A constant 1,000 N net force acts on the car over a distance of 50 m, causing the car to speed up. After it travels 50 m, the car moves with constant velocity. What is the total work done on the car over the 50 m distance it travels while speeding up?
 A. 25x10^4 J
 B. 5x10^4 J
 C. 15x10^4 J
 D. None of the above.
 32 A student applies a force to a cart to pull it up an inclined plane at a constant speed during a physics lab. A force of 20.8 N is applied parallel to the incline to lift a 3.00-kg loaded cart to a height of 0.450 m along an incline which is 0.636-m long. Determine the work done upon the cart and the subsequent potential energy change of the cart.
 A. 12 J
 B. 13.2 J
 C. 23.5 J
 D. None of the above.
 33 A 21.3-kg child positions himself on an inner-tube which is suspended by a 7.28-m long rope attached to a strong tree limb. The child and tube is drawn back until it makes a 17.4-degree angle with the vertical. The child is released and allowed to swing to and from. Assuming negligible friction, determine the child's speed at his lowest point in the trajectory.
 A. 2.56 m/s
 B. 3.56 m/s
 C. 12.56 m/s
 D. None of the above.
 34 Which of the following statements are true about work?
 A. Work is a form of energy.
 B. A Watt is the standard metric unit of work.
 C. Work is a time-based quantity; it is dependent upon how fast a force displaces an object.
 D. None of the above.
 35 A 1 kg ball is dropped from the top of a cliff and falls with a constant acceleration due to gravity (9.8 m/s2). Assume that effects of air resistance can be ignored. How much work has been done on the ball?
 A. A falling object always gains kinetic energy as it falls.
 B. An object can never have a negative kinetic energy.
 C. The work done on the ball equals the energy changed from PE to KE, or 98 J.
 D. None of the above.
 36 A car having a mass of 500 kg is initially traveling with a speed of 80 km/hr. It slows down at a constant rate, coming to a stop in a distance of 50 m. What is the net force on the car while it's coming to a stop?
 A. -12.4x10^3 N
 B. 2.4x10^3 N
 C. -2.4x10^3 N
 D. None of the above.
 37 An object at rest may have __________. Presume that the value of g is ~10 m/s/s.
 A. Energy
 B. Velocity
 C. Acceleration
 D. None of the above.
 38 A car having a mass of 500 kg is initially traveling with a speed of 80 km/hr. It slows down at a constant rate, coming to a stop in a distance of 50 m. If the car slows to a stop on level ground, is the work done on it recoverable?
 A. The KE of the cars motion is turned into heat energy (the car's tires, the brakes and the road get hot) so the work done on the car is not recoverable.
 B. Faster moving objects always have a greater kinetic energy.
 C. Kinetic energy is the form of mechanical energy which depends upon the position of an object.
 D. None of the above.
 39 A 221-gram ball is thrown at an angle of 17.9 degrees and a speed of 36.7 m/s from the top of a 39.8-m high cliff. Determine the impact speed of the ball when it strikes the ground. Assume negligible air resistance.
 A. 36.7 m/s
 B. 46.1 m/s
 C. 461 m/s
 D. None of the above.
 40 A car having a mass of 500 kg is initially traveling with a speed of 80 km/hr. It slows down at a constant rate, coming to a stop in a distance of 50 m. Where is the force applied?
 A. The force on the car causing it to stop is applied at the only point of contact the car has -- the ground! The ground pushes on the car opposite to the car's motion (that's the meaning of the minus sign above), causing it to stop. You can tell this, because a car's tires get hot from the friction forces between them and the road.
 B. Kinetic energy is the form of mechanical energy which depends upon the position of an object.
 C. Faster moving objects always have a greater kinetic energy.
 D. None of the above.
 41 During a construction project, a 2500 N object is lifted high above the ground. It is released and falls 10.0 meters and drives a post 0.100 m into the ground. The average impact force on the object is ____ Newtons. Presume that the value of g is ~10 m/s/s.
 A. 2500
 B. 25000
 C. 250,000
 D. None of the above.
 42 A baseball player catches a 163-gram baseball which is moving horizontally at a speed of 39.8 m/s. Determine the force which she must apply to the baseball if her mitt recoils a horizontal distance of 25.1 cm.
 A. 163 N
 B. 514 N
 C. 251 N
 D. None of the above.
 43 Which of the following statements are true about power?
 A. Powerful people or powerful machines are simply people or machines which always do a lot of work.
 B. Power refers to how fast work is done upon an object.
 C. If person A and person B do the same job but person B does it faster, then person A does more work but person B has more power.
 D. None of the above.
 44 Mia Kneezhirt jumps from a second story dorm room (h = 7.91 m) to the ground below. Upon contact with the ground, she allows her 62.4-kg body to come to an abrupt stop as her center of gravity is displaced downwards a distance of 89.2 cm. Calculate the average upward force exerted by the ground upon Mia's fragile body.
 A. 5243 N
 B. 5423 N
 C. 2423 N
 D. None of the above.
 45 Calculate the kinetic energy (KE) of a 1500-kg automobile with a speed of 30 m/s. If it accelerates to this speed in 20 s, what average power has been developed?
 A. 3.4 x 10 ^ 4 W
 B. 13.4 x 10 ^ 4 W
 C. 6.4 x 10 ^ 4 W
 D. None of the above.
 46 A 65.8-kg skier accelerates down an icy hill from an original height of 521 meters. Use the work-energy theorem to determine the speed at the bottom of the hill if... (a) no energy is lost or gained due to friction, air resistance and other non-conservative forces.  (b) 1.40*105 J of energy are lost due to external forces.
 A. (a) v = 101 m/s; (b) v = 77.2 m/s
 B. (a) v = 77.2 m/s; (b) v = 101 m/s
 C. (a) v = 151 m/s; (b) v = 87.2 m/s
 D. None of the above.
 47 A 1200 kg car and a 2400 kg car are lifted to the same height at a constant speed in a auto service station. Lifting the more massive car requires ____ work. Presume that the value of g is ~10 m/s/s.
 A. The same
 B. Less
 C. Twice as much
 D. None of the above.
 48 Pete Zaria applies a 11.9-Newton force to a 1.49-kg mug of root beer in order to accelerate it from rest over a distance of 1.42-m. Once released, how far will the mug slide along the counter top if the coefficient of friction is 0.728?
 A. 0.119 m
 B. 0.170 m
 C. 0.149 m
 D. None of the above.
 49 A 50-kg platform diver hits the water below with a kinetic energy of 5000 Joules. The height (relative to the water) from which the diver dove was approximately ____ meters. Presume that the value of g is ~10 m/s/s.
 A. 5
 B. 10
 C. 50
 D. None of the above.
 50 A 1 kg ball is dropped from the top of a cliff and falls with a constant acceleration due to gravity (9.8 m/s2). Assume that effects of air resistance can be ignored. What is the force (if any) that does work on the ball?
 A. It's the force of gravity that does work on the ball.
 B. F work is done on an object by a non-conservative force, then the object will either gain or lose kinetic energy.
 C. More massive objects always have a greater kinetic energy.
 D. None of the above.
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