Q&A Hero

Q: Strictly speaking, more fuel is consumed by your car if the air conditioner, headlights, or even a radio is turned on. This statement is A) false. B) true only if the car's engine is running. C) true.

Q: When wind encounters a wind turbine that produces energy, wind speed on the downside of the blades is A) slowed. B) speeded up. C) not affected.

Q: A light aluminum ball and a heavy lead ball of the same size roll down an incline. When they are halfway down the incline, they will have identical A) kinetic energies. B) potential energies. C) momentum. D) inertias. E) none of the above

Q: A block of ice sliding down an incline has half its maximum kinetic energy A) at the top. B) at the bottom. C) halfway down. D) need more information

Q: After rolling halfway down an incline, a marble's kinetic energy is A) less than its potential energy. B) greater than its potential energy. C) the same as its potential energy.

Q: The bob of a simple pendulum has its maximum kinetic energy at the A) top of its swing. B) bottom of its swing. C) midpoint between top and bottom. D) at all points along its path of swing.

Q: A ball rolling down an incline has its maximum kinetic energy at A) the top. B) halfway down. C) three-quarters of the way down. D) the bottom.

Q: A ball rolling down an incline has its maximum potential energy at A) the top. B) a quarter of the way down. C) halfway down. D) the bottom.

Q: Two identical arrows, one with twice the speed of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates A) the same distance. B) two times as far. C) four times as far. D) more than four times as far. E) none of the above

Q: Two identical arrows, one with twice the kinetic energy of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates A) the same distance. B) twice as far. C) four times as far. D) more than four times as far. E) none of the above

Q: A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is A) 2,500 N. B) 25,000 N. C) 250,000 N. D) 2,500,000 N.

Q: Which requires the most amount of work by the brakes of a car? A) slowing down from 100 km/h to 70 km/h B) slowing down from 70 km/h to a stop C) equal amounts for both

Q: If the speed of a bicycle is reduced to half before skidding to a stop, it will skid A) one-eighth as far. B) one-fourth as far. C) one-half as far. D) none of the above

Q: About 40 J is required to push a crate 4 m across a floor. If the push is in the same direction as the motion of the crate, the force on the crate is about A) 4 N. B) 10 N. C) 40 N. D) 160 N.

Q: A cannonball has more kinetic energy than the recoiling cannon from which it is fired because the force on the ball A) is more concentrated. B) meets less resistance than the cannon on the ground. C) acts over a longer distance.

Q: A motorcycle moving at 50 km/h skids 10 m with locked brakes. How far will it skid with locked brakes when traveling at 150 km/h? A) 10 m B) 30 m C) 50 m D) 90 m

Q: A bicycle that travels four as fast as another when braking to a stop will skid A) twice as far. B) four times as far. C) eight times as far D) sixteen times as far. E) depends on the mass of the bike

Q: A bicycle that travels twice as fast as another when braking to a stop will skid A) twice as far. B) four times as far. C) eight times as far D) sixteen times as far. E) depends on the bike's mass

Q: When Joshua brakes his speeding bicycle to a stop, kinetic energy is transformed to A) potential energy. B) energy of motion. C) energy of rest. D) heat.

Q: Two identical particles move toward each other, one twice as fast as the other. Just before they collide, one has a kinetic energy of 25 J and the other 50 J. At this instant their total kinetic energy is A) 25 J. B) 50 J. C) 75 J. D) none of the above E) need more information

Q: If a Ping-Pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the Ping-Pong ball must be A) less than the golf ball. B) more than the golf ball. C) both the same D) need more information

Q: Neglecting air resistance, Sammy Smarts on a high ladder releases a ball that strikes the ground with 100 J of kinetic energy. If he were to instead throw the ball straight upward, it will soon reach the ground with a kinetic energy of A) less than 100 J. B) 100 J. C) more than 100 J.

Q: Which has greater kinetic energy? A) a car traveling at 30 km/hr B) a car of half the mass traveling at 60 km/hr C) both the same D) need more information

Q: Danny Diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of A) 10 J. B) 500 J. C) 510 J. D) 5000 J. E) more than 5000 J.

Q: A melon is projected into the air with 100 J of kinetic energy in the presence of air resistance. When it returns to its initial level its kinetic energy is A) less than 100 J. B) more than 100 J. C) 100 J. D) need more information

Q: A melon is tossed straight upward with 100 J of kinetic energy. If air resistance is negligible the melon will return to its initial level with a kinetic energy of A) less than 100 J. B) more than 100 J. C) 100 J. D) need more information

Q: A feather and a coin dropped in a vacuum fall with equal A) forces due to gravity. B) accelerations. C) kinetic energies. D) none of these

Q: Two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has A) twice the kinetic energy. B) four times the kinetic energy. C) eight times the kinetic energy. D) none of the above

Q: An object that has kinetic energy must be A) moving. B) falling. C) at an elevated position. D) at rest. E) none of the above

Q: The ram of a pile driver drops onto the top of an iron beam, driving it partway into the ground. The distance that the beam sinks into the ground depends on the A) initial height of the ram. B) initial potential energy of the ram. C) kinetic energy of the ram when it first hits the beam. D) all of the above

Q: A 2-kg box of taffy candy has 40 J of potential energy relative to the ground. Its height above the ground is A) 1 m. B) 2 m. C) 3 m. D) 4 m. E) none of the above

Q: A 2-kg ball is held 4 m above the ground. Relative to the ground its potential energy is A) 6 J. B) 8 J. C) 32 J. D) 80 J. E) more than 80 J.

Q: A clerk can lift cylindrical packages 1 meter vertically, or can roll them up a 2-meter-long ramp to the same elevation. With the ramp, the applied force required is about A) half as much. B) the same. C) twice as much. D) four times as much.

Q: When a drawn bow of potential energy 40 J is fired, the arrow will ideally have a kinetic energy A) less than 40 J. B) more than 40 J. C) of 40 J.

Q: A crate of grapes lifted 10 meters gains 200 J of potential energy. If the same crate is instead lifted 20 meters, its gain in potential energy is A) half as much. B) the same. C) twice as much. D) four times as much. E) more than four times as much.

Q: Relative to an initial height, an object raised twice as high has a gravitational potential energy A) half as much B) twice as much. C) four times as much. D) need more information

Q: An object has gravitational potential energy due to its A) speed. B) acceleration. C) momentum. D) location. E) none of the above

Q: The center of a long uniform log is raised to shoulder level while the other end is on the ground. If instead, the end of the log is raised to shoulder level, the work required is A) half. B) the same. C) twice.

Q: A toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed using 1000 J of work, is A) 20 W. B) 50 W. C) 100 W. D) 1000 W. E) 20,000 W.

Q: Both a 50-kg sack is lifted 2 meters from the ground and a 25-kg sack is lifted 4 meters in the same time. The power expended in raising the 50-kg sack is A) twice as much as the 25-kg sack. B) half as much as the 25-kg sack. C) the same. D) need more information

Q: The power required to exert 4-N force over 3 meters in 2 seconds is A) 4 W. B) 6 W. C) 8 W. D) 12 W. E) none of the above

Q: The power expended doing 100 J of work in 50 s is A) 1/2 W. B) 2 W. C) 4 W. D) 50 W. E) 5,000 W.

Q: If you do work on a skateboard loaded with friends in one-third the usual time, you expend A) one third as much power. B) the usual power. C) three times the usual power. D) need more information.

Q: The amount of work done on a heavy box carried by Nellie across a room at a constant speed A) depends on the weight of the box. B) depends on the distance walked. C) depends on both weight of the box and distance walked. D) is none. E) none of the above

Q: Which task requires more work? A) lifting the 50-kg sack 2 meters B) lifting the 25-kg sack 4 meters C) both require the same D) need more information

Q: One kilowatt-hour represents A) 1 N. B) 60 N/s. C) 60,000 W. D) 3.6 million joules. E) none of these

Q: The unit kilowatt-hour is a unit of A) energy. B) momentum. C) power. D) time.

Q: A 1000-kg car and a 2000-kg car are hoisted to the same height. Raising the more massive car requires A) less work. B) as much work. C) twice as much work. D) four times as much work. E) more than four times as much work.

Q: No work is done by gravity on a bowling ball that rolls along a bowling alley because A) no force acts on the ball. B) little distance is covered by the ball. C) the force on the ball is at right angles to the ball's motion. D) the ball's speed remains constant.

Q: The work you do when pushing a shopping cart a given distance while applying twice as much force is A) half as much. B) twice as much. C) four times as much. D) the same amount.

Q: The work you do when pushing a shopping cart twice as far while applying twice the force is A) half as much. B) twice as much. C) four times as much. D) the same amount.

Q: The work you do when pushing a shopping cart twice as far while applying the same force is A) half as much. B) twice as much. C) four times as much. D) the same amount.

Q: The work done in pushing a TV set a distance of 2 m with an average force of 20 N is A) 2 J. B) 10 J. C) 20 J. D) 40 J. E) 800 J.

Q: A cannonball following a parabolic path explodes into fragments. The momentum of the fragments A) continue along the path as if the explosion didn't occur. B) cancels to zero by vector addition. C) both of these D) neither of these

Q: When a vertically falling firecracker bursts, the vector sum of momentum fragments A) in the horizontal direction cancels to zero. B) in the vertical direction equals the momentum of the firecracker before bursting. C) both of these D) neither of these

Q: A firecracker bursts while freely falling. The combined momentum of its fragments A) equals the momentum of the firecracker at the time of burst B) cancels to the firecracker's momentum at the time of bursting. C) cancels to zero. D) none of the above

Q: Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The magnitude of momentum for the combined wreck is A) the same as the magnitude of momentum of either car before collision. B) less than the magnitude of momentum of either car before collision. C) greater than the magnitude of momentum of either car before collision. D) none of the above

Q: Two vehicles with equal magnitudes of momentum traveling at right angles to each other undergo an inelastic collision. The combined wreck moves in a direction A) parallel to either of the cars before collision. B) at 45 degrees to the direction of either car before collision. C) at some angle other than 45 degrees.

Q: Two identical objects in outer space, one moving at 2 m/s, the other at 1 m/s, have a head-on collision and stick together. Their combined speed after the collision is A) 0.5 m/s. B) 0.33 m/s. C) 0.67 m/s. D) 1.0 m/s. E) none of the above

Q: Two 5000-kg rail cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple, and roll together with a combined momentum of A) zero. B) 5000 kg m/s. C) 10,000 kg m/s. D) 15,000 kg m/s.

Q: Two identical freight cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple together, and roll away in the direction of A) the slower car. B) the faster car. C) neither, for they stop.

Q: A red car has a head-on collision with an approaching blue car with the same magnitude of momentum. A green car driving with the same momentum as the other cars collides with an enormously massive wall. Which of the three cars will experience the greatest impulse? A) red car B) blue car C) green car D) all the same

Q: A sandbag motionless in outer space is hit by a three-times-as massive sandbag moving at 12 m/s. They stick together and move at a speed of A) 3 m/s. B) 4 m/s. C) 6 m/s. D) 8 m/s. E) none of the above

Q: A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track. They collide and stick. The combined mass moves at A) 0 m/s. B) 1/2 m/s. C) 1/3 m/s. D) 1/6 m/s. E) 1.5 m/s.

Q: Consider massive gliders that slide friction-free along a horizontal air track. Glider A has a mass of 1 kg, a speed of 1 m/s, and collides with Glider B that has a mass of 5 kg and is at rest. If they stick upon collision, their speed after collision will be A) 1/4 m/s. B) 1/5 m/s. C) 1/6 m/s. D) 1 m/s. E) none of the above

Q: A 5000-kg freight car collides with a 10,000-kg freight car at rest. They couple upon collision and move at 2 m/s. What was the initial speed of the 5000-kg car? A) 4 m/s B) 5 m/s C) 6 m/s D) 8 m/s E) none of the above

Q: A 5000-kg freight car moving at 2 m/s collides with a 10,000-kg freight car at rest. They couple upon collision and move away at A) 2 m/s. B) 1 m/s. C) 2/3 m/s. D) 1/3 m/s.

Q: Two identical gliders slide toward each other on an air track. One moves at 1 m/s and the other at 2 m/s. They collide, stick, and moves at A) 1/2 m/s. B) 1/3 m/s. C) 1/6 m/s. D) 3/4 m/s. E) 1.5 m/s.

Q: A golf ball moving forward with 1 unit of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball is set in motion with a momentum of A) less than 1 unit. B) more than 1 unit. C) 1 unit. D) not enough information

Q: If all people, animals, trains and trucks all over the world began to walk or run towards the east (opposite the direction of Earth's spin), then A) Earth would spin a bit faster. B) Earth would spin a bit slower. C) Earth's spin would not be affected at all.

Q: A fan attached to an ice sailcraft stalled on a windless day blows air into the sail that bounces backward upon impact. The boat A) moves in the direction of the wind impact force. B) does not move by this wind impact. C) moves, but in the opposite direction of the wind impact force.

Q: A 5-kg shark swimming at 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the shark after his meal is A) 1/2 m/s. B) 1/5 m/s. C) 1/6 m/s. D) 2/3 m/s. E) 3/2 m/s.

Q: A 5-kg fish swimming at 1 m/s swallows an absent-minded 1-kg fish at rest. The speed of the larger fish after lunch is A) 1/2 m/s. B) 2/5 m/s. C) 5/6 m/s. D) 6/5 m/s. E) 1 m/s.

Q: A 2-kg rifle that is suspended by strings fires a 0.01-kg bullet at 200 m/s. The recoil velocity of the rifle is about A) 0.001 m/s. B) 0.01 m/s. C) 0.1 m/s. D) 1 m/s. E) none of these

Q: A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball initially at rest. The bowling ball and putty then move with a momentum of A) 0 kg m/s. B) 1 kg m/s. C) 2 kg m/s. D) 5 kg m/s. E) more than 5 kg m/s.

Q: An open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically. As water accumulates in the car, the car's speed A) increases. B) decreases. C) doesn't change. D) need more information

Q: If a monkey floating in outer space throws his hat away, the hat and the monkey will both A) move away from each other, but at different speeds. B) move away from each other at the same speed. C) move a short distance and then slow down. D) move a short distance and then go faster. E) come to a stop after a few minutes.

Q: Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet? A) zero B) half the sum of their original momentums C) twice the sum of their original momentums D) need more information

Q: Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be A) zero. B) the same as before. C) small, but noticeable.

Q: An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will A) move in the opposite direction at 20 m/s. B) move in the opposite direction at a lower speed. C) move in the opposite direction at a higher speed. D) none of the above