Chapters 6-7
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) 6 m/s B)5 m/s C)8 m/s D) 4 m/s E)none of the above
A
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.
A
A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the A)cannon has much more mass than the cannonball. B)force against the cannon is smaller than against the ball. C)momentum of the cannon is smaller. D)momentum is mainly concentrated in the cannonball.
A
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
A
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
B
A freight train rolls along a track with considerable momentum. If it rolls at the same speed but has twice as much mass, its momentum is A) zero. B) twice. C) four times as much. D) unchanged.
B
A karate chop is more effective if one's hand A) follows through upon impact. B) bounces upon impact. C) extends the time upon impact
B
Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard. The reason he doesn't slip off the skateboard is due to A)momentum change. B)friction between his feet and the board. C)inertia in motion.
B
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
B
If several balls are thrown straight up with different initial speeds, the quantity that will have the same value along their paths is their A)time of travel. B)acceleration. C)maximum height. D) initial momentum. E) none of the above
B
The average braking force of a 1000-kg car moving at 10 m/s braking to a stop in 5 s is You Answered A)5000 N. B)2000 N. C)3000 N. D)1000 N. E)4000 N.
B
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.
B
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
B
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is A)greater with the haystack. B) both the same C)greater with the brick wall.
B
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the stopping force is A) greater with the haystack. B) greater with the brick wall. C) both the same
B
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
B
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.
C
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
C
A cannon recoils while firing a cannonball. The speed of the cannon's recoil is relatively small because the A) force against the cannon is smaller than against the ball. B) momentum is mainly concentrated in the cannonball. C) cannon has much more mass than the cannonball. D) momentum of the cannon is smaller.
C
A firecracker bursts while freely falling. The combined momentum of its fragments A) cancels to the firecracker's momentum at the time of bursting. B) cancels to zero. C) equals the momentum of the firecracker at the time of burst D) none of the above
C
A firecracker bursts while freely falling. The combined momentum of its fragments A)cancels to the firecracker's momentum at the time of bursting. B)cancels to zero. C) equals the momentum of the firecracker at the time of burst D) none of the above
C
You're driving down the highway and a bug spatters into your windshield. Which undergoes the greater change in momentum during the time of contact? A) the bug B)your car C) both the same
C
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.
D
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.
D
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)10,000 kg m/s. B)15,000 kg m/s. C) zero. D) 5000 kg m/s.
D
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)10,000 kg m/s. B)15,000 kg m/s. C) zero. D)5000 kg m/s.
D
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
A
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.
A
A heavy truck and a small car rolling down a hill at the same speed are forced to stop in the same amount of time. Compared with the force that stops the car, the force needed to stop the truck is A) greater. B) smaller. C) the same.
A
A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. Both move with a combined momentum of A) 1 unit. B) more than 1 unit. C) less than 1 unit. D) need more information
A
A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. Both move with a combined momentum of A)1 unit. B) more than 1 unit. C) less than 1 unit. D) need more information
A
Compared with falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the A)stopping time is longer on the carpet. B) stopping time is shorter on the carpet. C) carpeted floor provides a smaller impulse. D) carpet provides a smaller impulse and a longer time.
A
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) 1/6 m/s. B) 1/4 m/s. C) 1 m/s. D) 1/5 m/s. E) none of the above
A
Padded dashboards in cars are safer in an accident than non-padded ones because passengers hitting the dashboard encounter A) lengthened time of contact. B) shorter time of contact. C) decreased impulse. D) increased momentum.
A
The impulse-momentum relationship is a direct result of A) Newton's 2nd law. B) Newton's 3rd law. C) Newton's law of gravity. D) Newton's 1st law.
A
The speed of a 4-kg ball with a momentum of 12 kg m/s is A) 3 m/s. B) 4 m/s. C) 12 m/s. D) 48 m/s. E) none of the above
A
The unit kilowatt-hour is a unit of A) energy. B) momentum. C) power. D) time.
A
To catch a fast-moving ball, you extend your hand forward before contact with the ball and let it ride backward in the direction of the ball's motion. Doing this reduces the force of contact on your hand principally because the A)time of contact is increased. B)time of contact is decreased. C)force of contact is reduced. D)relative velocity is less. E)none of the above
A
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
A
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 faster car. B) the slower car. C) neither, for they stop.
A
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 faster car. B) the slower car. C) neither, for they stop.
A
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
A
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) at 45 degrees to the direction of either car before collision. B) parallel to either of the cars before collision. C) at some angle other than 45 degrees.
A
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)at 45 degrees to the direction of either car before collision. B)parallel to either of the cars before collision. C)at some angle other than 45 degrees.
A
When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, the speed of the skateboard A) decreases. B) increases. C) neither decreases nor increases
A
When bullets are fired from an airplane in the forward direction, the momentum of the airplane is A)decreased. B)increased. C)unchanged.
A
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
A
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.
B
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
B
A softer landing occurs when an falling object bounces from a surface A)quickly. B)in a extended time. C)either of these D)neither of these
B
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.
B
Acrobat Bart at the circus drops vertically onto the end of a see-saw, with his partner Art equidistant from the fulcrum at the other end. Art is propelled straight upward a distance twice that of Bart's dropping distance. Neglecting inefficiencies we see A) the masses of Art and Bart are equal. B) Art has half the mass of Bart. C) need more information
B
It is correct to say that impulse is equal to A) momentum. B) a corresponding change in momentum. C) force multiplied by the distance it acts. D) velocity multiplied by time.
B
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.
B
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)small, but noticeable. B)zero. C)the same as before.
B
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
B
The average braking force of a 1000-kg car moving at 10 m/s braking to a stop in 5 s is A) 1000 N. B) 2000 N. C) 3000 N. D) 4000 N. E) 5000 N.
B
The change in momentum that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s is A) 4 kg m/s. B)6 kg m/s. C) 8 kg m/s. D) 2 kg m/s.
B
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
B
Which of the following has the largest momentum relative to Earth's surface? A) a tightrope walker crossing Niagara Falls B) a pickup truck speeding along a highway C) a Mack truck parked in a parking lot D) the Science building on campus E) a mouse running across your room
B
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
C
A motorcycle of mass 100 kilograms slowly rolls off the edge of a cliff and falls for three seconds before reaching the bottom of a gully. Its momentum upon hitting the ground is A) 1,000 kg m/s. B) 2,000 kg m/s. C) 3,000 kg m/s. D) 4,000 kg m/s. E) 9,000 kg m/.
C
A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. Both move with a combined momentum of A) less than 1 unit. B) more than 1 unit. C) 1 unit. D) need more information
C
A same-size iron ball and wooden ball are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater A) speed. B) acceleration. C) momentum. D) all of the above E) none of the above
C
If you can't avoid being hit by a fast-moving object, you'll suffer a smaller contact force if you can extend that force over a A)shorter time. B) both the same C) longer time.
C
If you can't avoid being hit by a fast-moving object, you'll suffer a smaller contact force if you can extend that force over a A)shorter time. B)both the same C)longer time.
C
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.
C
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.
C
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
C
The change in momentum that occurs when a 1.0 kg ball traveling at 4.0 m/s strikes a wall and bounces back at 2.0 m/s is A) 2 kg m/s. B) 4 kg m/s. C) 6 kg m/s. D) 8 kg m/s.
C
The mass of a ball moving at 3 m/s with a momentum of 48 kg m/s is A) 4 kg. B) 12 kg. C) 16 kg. D) 144 kg. E) none of these
C
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.
C
To catch a fast-moving ball, you extend your hand forward before contact with the ball and let it ride backward in the direction of the ball's motion. Doing this reduces the force of contact on your hand principally because the A) force of contact is reduced. B) relative velocity is less. C) time of contact is increased. D) time of contact is decreased. E) none of the above
C
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
C
When a boxer is moving away from a punch, the force experienced is reduced because A) the force is less effective. B) momentum transfer is reduced. C) the time of contact is increased. D) all of the above
C
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.
C
When a vertically falling firecracker bursts, the vector sum of momentum fragments A) in the vertical direction equals the momentum of the firecracker before bursting. B)in the horizontal direction cancels to zero. C)both of these D) neither of these
C
When a vertically falling firecracker bursts, the vector sum of momentum fragments A) in the vertical direction equals the momentum of the firecracker before bursting. B) in the horizontal direction cancels to zero. C) both of these D) neither of these
C
Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is A) greater with the haystack. B) greater with the brick wall. C) both the same
C
Which has the greater momentum when moving? A)a container ship B)a bullet C)either of these depending on speed
C
Which has the greater momentum when moving? A) a container ship B) a bullet C) either of these depending on speed
C
Which produces more force: driving into a very massive concrete wall with no "give," or having a head-on collision with an identical car moving toward you at the same speed? A) car B) wall C) both the same D) need more information
C
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
C
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
C
A car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has A) more mass. B) more momentum. C) less stopping distance. D) all of the above E) none of the above
D
A car traveling along the highway brakes to a stop over a certain distance. More braking force is required if the car has A) more momentum. B) less stopping distance. C)more mass. D)all of the above E)none of the above
D
A circus diver drops from a high pole into water far below. When he is halfway down A) his potential energy is halved. B) he has gained an amount of kinetic energy equal to half his initial potential energy. C) his kinetic energy and potential energy are equal. D) all of the above E) none of the above
D
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
D
A motorcycle of mass 100 kilograms slowly rolls off the edge of a cliff and falls for three seconds before reaching the bottom of a gully. Its momentum upon hitting the ground is A) 1,000 kg m/s. B) 9,000 kg m/. C) 2,000 kg m/s. D)3,000 kg m/s. E)4,000 kg m/s.
D
An object has gravitational potential energy due to its A) speed. B) acceleration. C) momentum. D) location. E) none of the above
D
As Bronco Brown steps off a hovering high-flying helicopter and falls through the air, he experiences A)an increasing speed. B)a decreasing acceleration. C)an impulse. D)all of the above
D
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
D
It is correct to say that impulse is equal to A) momentum. B) velocity multiplied by time. C) force multiplied by the distance it acts. D) a corresponding change in momentum.
D
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
D
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.
D
When Peter tosses an egg against a sagging sheet, the egg doesn't break due to A) reduced impulse. B) reduced momentum. C) both of these D) neither of these
D
When you jump from an elevated position you usually bend your knees upon reaching the ground, which makes the time of the contact about 10 times that of a stiff-legged landing. In this way the average force your body experiences is A)more than 1/10 as great. B)about 10 times as great. C)less than 1/10 as great. D)about 1/10 as great.
D
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)1.5 m/s. B)0 m/s. C)1/2 m/s. D)1/6 m/s. E)1/3 m/s.
E
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)8 m/s. D) 6 m/s. E)none of the above
E