Q&A Hero

Q: Two people are balanced on a seesaw. If one person leans inward toward the center of the seesaw, that person's end of the seesaw tends to A) rise. B) fall. C) stay at the same level. D) need more information

Q: To rotate a stubborn screw, it is best to use a screwdriver that has a A) wide handle. B) long handle. C) smooth handle. D) none of the above

Q: A ball gains speed while rolling down a hill due mainly to A) its rotational inertia. B) its angular acceleration. C) a balanced torque. D) an unbalanced torque.

Q: For a system in mechanical equilibrium, the resultant A) force must be zero. B) torque must be zero. C) both of these D) none of these

Q: If you place a pipe over the end of a wrench when trying to rotate a stubborn bolt, effectively making the wrench handle twice as long, you'll multiply the torque by A) two. B) four. C) eight.

Q: A ball that gains speed as it rolls down a hill experiences a A) net torque. B) net force. C) both of these D) neither of these

Q: If Alex wishes to rotate his skateboard, then he must apply a A) torque. B) rotational maneuver. C) pause before bearing down on the board.

Q: A torque acting on an object tends to produce A) equilibrium. B) rotation. C) linear motion. D) velocity. E) a center of gravity.

Q: Compared with a force, a torque involves A) rotation. B) leverage. C) distance from an axis of rotation. D) all the above

Q: Which tin can will roll down an incline in the shortest time, one filled with water or one filled with ice? (Hint: water 'slides' inside the can.) A) with water B) with ice C) both the same D) need more information

Q: Which jar will roll down an incline in the shortest time, an empty one or one filled with peanut butter? A) the empty jar B) both reach the bottom at the same time C) the filled jar D) need more information

Q: Stand a broom upright on the end of its pole and let it topple to the floor. Repeat, but with the bristles end on the floor. The faster fall will be the broom standing on its A) pole-end. B) bristles-end. C) the same either way.

Q: A vertically-held sledge hammer is easier to balance when the heavier end is A) on your hand. B) at the top, away from your hand. C) the same either way

Q: Stand a meterstick on its end and let it rotate to the floor. If you attach a heavy glob of clay to its upper end and repeat, the time to fall will be A) shorter. B) longer. C) the same.

Q: A vertically-held sledge hammer is easier to balance when the heavier end is A) on your hand. B) at the top, away from your hand. C) same either way

Q: A ring, a disk, and a solid sphere begin rolling down a hill together. Which reaches the bottom first? A) ring B) disk C) sphere D) all reach the bottom at the same time E) need more information

Q: A ring and a disk both at rest roll down a hill together. Which rolls slower? A) ring B) disk C) depends on the masses D) both roll at the same speed E) need more information

Q: A coin and a ring roll down an incline at the same time. The one to first reach the bottom is the A) ring. B) coin. C) both reach the bottom at the same time

Q: A flywheel's diameter is twice that of another of the same shape and mass. Rotational inertia of the larger flywheel is A) two times greater. B) four times greater. C) the same as the other's. D) half.

Q: Consider two flywheels of the same size and shape, but one with twice the mass. Rotational inertia of the more massive one is A) two times greater. B) four times greater. C) the same as the other one. D) half.

Q: A tightrope walker more easily balances on a tight wire if her pole A) is held high. B) droops. C) is short but heavy.

Q: Which of these animals has a quicker stride? A) giraffe B) horse C) cat D) mouse

Q: The rotational inertia of a pencil is greatest about an axis A) along its length, where the lead is. B) about its midpoint, like a propeller. C) about its end, like a pendulum.

Q: An industrial flywheel has a greater rotational inertia when most of its mass is A) nearer the rim. B) nearer the axis. C) uniformly spread out as in a disk.

Q: You can swing your legs to and fro more frequently when your legs are A) straight. B) bent. C) same either way

Q: The rotational inertia of your leg is greater when your leg is A) straight. B) bent. C) same either way

Q: If you're on a Ferris wheel at a carnival, seated 10 m from the Ferris wheel's axis that makes a complete rotation each minute, your linear speed is A) 10 m/min. B) 31.4 m/min. C) 62.8 m/min. D) 100 m/min. E) need more information

Q: The net force exerted on a car traveling in a circular path at constant speed is A) directed forward, in the direction of travel. B) directed toward the center of the curve. C) zero because the car is not accelerating. D) none of the above

Q: Consider a string with several rocks tied along its length at equally spaced intervals. You whirl the string overhead so that the rocks follow circular paths. Compared with a rock at the end of the string, a rock at the middle moves A) half as fast. B) twice as fast. C) at the same linear speed.

Q: The circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second then its linear speed is A) 1 m/s. B) 2 m/s. C) 3 m/s. D) 3.14 m/s. E) 6.28 m/s.

Q: The tapered shape of the wheel rims that ride on railroad tracks allows opposite wheels to A) in effect, vary their diameters. B) travel at different linear speeds for the same rotational speed. C) both of these D) none of these

Q: Each rolling wheel of a railroad train is tapered. Compared with the wide part, the narrow part of the wheel has a tangential speed that is A) less. B) greater. C) the same for both.

Q: When a train makes a curve, a tapered wheel rim is able to A) cover different distances per revolution. B) maintain a fixed rotational speed. C) reduce differences in angular speeds.

Q: When railroad tracks make a curve, the outer track is longer. This means a wheel that rides on the outer track needs to somehow A) roll slower than the wheel on the inner track. B) maintain the same speed as the wheel on the inner track. C) roll faster than the wheel on the inner track.

Q: Your pet hamster sits on a record player that has constant angular speed. If the hamster moves to a point twice as far from the center, then its linear speed A) doubles. B) halves. C) remains the same.

Q: If a turntable's rotational speed is doubled, then the linear speed of a pet hamster sitting on the edge of the record will A) double. B) halve. C) remain the same.

Q: Which horse moves faster in m/s on a merry-go-round? A) one near inner rail B) one near outer rail C) both move at the same speed in m/s.

Q: Horses with the greatest linear speed on a merry-go-round are located A) near the center. B) near the outside. C) anywhere, because they all move at the same speed.

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: Newton's Cradle consists of an aligned row of identical elastic balls suspended by strings so they barely touch one another. When two balls are raised from one end and released, they strike the row and two balls pop out from the other end. If instead, one ball popped out with twice the speed of the two, this would violate A) momentum conservation. B) energy conservation. C) both of these D) none of these

Q: A piece of taffy slams into and sticks to an identical piece of taffy at rest. The momentum of the combined pieces after the collision is the same as before the collision, but this is not true of the kinetic energy, which partly degrades into heat. What percentage of the kinetic energy becomes heat? A) 0% B) 25% C) 50% D) 75% E) need more information

Q: A golf ball is thrown at and bounces backward from a massive bowling ball that is initially at rest. After the collision, compared to the golf ball, the bowling ball has more A) momentum, but less kinetic energy. B) kinetic energy, but less momentum. C) momentum and more kinetic energy. D) need more information

Q: Compared to the recoiling cannon, a fired cannonball has a A) greater momentum. B) greater kinetic energy. C) smaller speed. D) all of the above

Q: Two 2-m/s pool balls roll toward each other and collide. Suppose after bouncing apart each moves at 4 m/s. This collision violates the conservation of A) momentum. B) energy. C) both momentum and energy. D) none of the above

Q: A roller skate at rest may have A) speed. B) velocity. C) momentum. D) energy.

Q: When you and your snowboard are in motion, which of the following can be zero? A) momentum B) kinetic energy C) mass D) inertia E) none of the above

Q: When a cannon is fired, it recoils as the cannonball is set in motion. The cannon and cannonball ideally acquire equal A) but opposite amounts of momentum. B) amounts of kinetic energy. C) both of these D) neither of these

Q: If the speed of a motor scooter doubles, which of the following also doubles? A) momentum B) kinetic energy C) acceleration D) all of the above

Q: If an all-electric car has kinetic energy, then it also must have A) impulse. B) momentum. C) acceleration. D) force. E) none of the above

Q: A moving object has A) speed. B) velocity. C) momentum. D) energy. E) all of these

Q: Impulse involves the time that a force acts, whereas work involves the A) distance that a force acts. B) time and distance that a force acts. C) acceleration that a force produces.

Q: A primary difference between momentum and kinetic energy is A) momenta can cancel; kinetic energy cannot. B) kinetic energy can cancel; momenta cannot. C) either of the above depending on circumstances D) none of the above