Physical Science exam #3

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a 5000 kg freight car crashes into a 10,000 kg freight car at rest. they couple upon collision and move with a speed of 2 m/s. what was the initial speed of the 5000 kg freight car

6 m/s

the greater effciency with the curved blades of a pelton wheel is due to

bouncing

the impulse momentum relationship is a direct result of

newtons second law

When a boxer moves into an oncoming punch, the force experienced is

increased

according to the impulse momentum relationship ft= change in mv, a falling bungee jumper has momentum which is reduced by the force F exerted by the bungee cord. if v is the speed of the jumper, then m in the equation is the mass of the

jumper

If a charging rhinoceros has momentum, it must also have

kinetic energy.

jogging jake runs along the top of a moving flatcar in the direction of motion of the flatcar. if he runs in the opposite direction, the combined momentum of jake and the flatcar relative to a observer at rest will be

less

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

less than 100 J.

An object may have potential energy because of its

location

When you can't escape being hit by a fast-moving object, you'll suffer a smaller force if the collision time is

long

a karate expert executes a swift blow and breaks a cement block with her bare hand. the magnitude of the force on her hand is

the same as the force applied to the block

Just after a big fish swallows a small fish, the momentum of the two-fish system is

the same before and after lunch

When a boxer is moving away from a punch, the force experienced is reduced because

the time of contact is increased

the conservation of momentum is most closely related to newtons

third law

A shopping cart moves with a kinetic energy of 40 J. If it moves at twice the speed, its kinetic energy is

160j

a peice of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball initially rest. after the putty sticks to the ball, both move with a combined momentum of

1 unit

Two billiard balls having the same mass roll toward each other at the same speed. What is the net momentum of the two-ball system?

0 kg m/s

When a 100-kg astronaut ejects 0.1 kg of gas at a speed of 50 m/s from her propulsion pistol, her recoil speed is

0.05 m/s

a 2 kg rifle is horizontally suspended by a pair of strings so that recoil can be measured. the rifle fires a 0.001 kg bullet at a speed of 200 m/s. the recoil velocity of the rifle is about

0.1 m/s

Two identical freight cars roll without friction towards each other on a level track. One car rolls at 2 m/s and the other car rolls at 1 m/s. After the cars collide, they couple and roll together with a speed of

0.5 m/s

a 30 kg girl on friction-free roller blades pushes away a 25 kg boy also on rollerblades at 1 m/s. the girls speed is

0.83 m/s

a 1 kg chunk of putty moving at 1 m/s collides and sticks to a 5 kg bowling ball initially at rest. the bowling ball and putty move with a momentum of

1 kg m/s

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

1/2 m/s

a 1kg glider and a 2kg glider both slide toward each other at 1 m/s on an air track. when they collide and stick, the combined-glider spped is

1/3 m/s

Consider 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, which has a mass of 5 kg and is at rest. If they stick upon collision the speed the combined gliders will be

1/6 m/s

a 1 kg chunk of putty moving at 1 m/s collides and sticks to a 5 kg bowling ball that is initially at rest in space. the bowling ball and putty are then set in motion with a speed of

1/6 m/s

a 5 kg fish swimming 1 m/s swallows an absent-minded 1 kg fish swimming toward it at 4 m/s. the speed of the larger fish after lunch is

1/6 m/s

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

100 J.

It takes 40 J to push a large crate 4 m across a floor. The force exerted on the crate is

10N

what is the mass of a ball moving at 4 m/s with a momentum of 48 kg m/s

12 kg

What is the speed of a 6-kg ball with a momentum of 72 kg∙m/s?

12 m/s

what is the mass of a ball moving at 3 m/s with a momentum of 48 kg m/s

16 kg

a 1000 kg truck moving at 10 m/s that brakes to a stop in 5s has an average braking force of

2000 N

A 2-kg mass that weighs 20 N has 40 J of potential energy relative to the ground. What is its height?

2m

What is the speed of a 4-kg ball with a momentum of 12 kg∙m/s?

3 m/s

A music console is pushed 2 m by a force of 20 N. The work done on the console is

40 J.

A bow is drawn so that it has 40 J of potential energy. When the arrow is fired its kinetic energy is ideally

40 j

a 5 kg fish swimming at a speed of 1 m/s swallows an absent-minded 1 kg fish at rest. the speed of the larger fish after lunch is

5/6 m/s

a boxer punches a sheet of paper in midair from rest to a speed of 40 m/s in 0.05 s. if the mass of the paper is 0.01 kg, the force of the punch on the paper is

8.0 N

A 2-kg mass weighs 20 N and is held 4 m above the ground. Its potential energy relative to the ground is

80j

Which has greater kinetic energy: a car traveling at 30 km/h or another car of half the mass traveling at 60 km/h?

The 60-km/h car

An astronaut floating alone in outer space throws a baseball. If the ball moves away at 20 m/s, the astronaut will move in the opposite direction at

a lower speed

which of the following has the largest momentum relative to earth?

a pickup truck speeding along a highway

If a monkey floating in outer space throws his hat away, the hat and the monkey will both move

away from each other, but at different speeds

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

about 10 times

The force of a falling apple hitting the ground depends upon

all of the above

The massive ram of a pile driver falling from rest strikes a pile with a speed that depends on the

all of the above

a car traveling along the highway brakes to a stop. a greater breaking force is required when the car has

all of the above

a moving object has

all of the above

the amount of potential energy possesed by an elevated object is

all of the above

Bronco's speed increases after he dives from a hovering helicopter. Relative to an observer in the helicopter Bronco's momentum

also increases

When you simultaneously drop a light tennis ball and a heavy bowling ball, they hit the floor

at the same speed

Padded dashboards in cars are safer in an accident than non-padded ones because a person hitting the dash has

both of these

Whether a truck comes to a stop by crashing into a haystack or a brick wall, the impulse is

both the same

which of these two collisions is more damaging; driving into a concrete wall with no "give", or colliding head-on with an identical car moving toward you ar your same speed

both the same

while driving down the highway a mosquito spatters onto your windsheild. which undergoes the greater impulse

both the same

while driving down the highway a mosquito spatters onto your windshield. which undergoes the greater change in momentum during the time of contact.

both the same

while driving down the highway of a mosquito spatters onto your windsheild. which experiences the greater force of impact?

both the same, but with different consenquences

a karate chop is more effective if one's hand

bounces upon impact

When Peter tosses an egg against a sagging sheet, the egg doesn't break due to

neither of these

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

decreases

When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, the speed of the skateboard

decreases

When bullets are fired in a forward direction from a fighter aircraft, the momentum of the aircraft

decreases

Whereas impulse involves the time that a force acts, work involves the

distance that a force acts

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

doubled

which has the greater momentum when moving?

either of these depending on speed

The force of air impact upon the sail of a boat is greater if the air

encounters the sail head-on

the unit kilowatt hour is a unit of

energy

When Jean standing on slippery ice catches her leaping dog Daisy, the momentum of both Jean and Daisy after the catch is

equal to their combined momentum before the catch

the force that accelerates a rocker in outer space is exerted on the rocket by the

exhaust gases

The total momentum of a flock of identical birds could be zero only if the birds are

flying in different directions

When Freddy Frog drops vertically from a tree onto a horizontally-moving skateboard, he doesnt slip off the skateboard because of

friction between his feet and the board

a straw is used for a pea shooteer. when you blow through the straw the speed of the emerging pea will be greater if the straw is

full length

a heavy truck and a small car roll down a hill at the same speed and need to stop in the same amount of time. compared with the force to stop the car, the force needed to stop the truck is

greater

When an apple falls to the ground, momentum is transferred to the ground. The momentum absorbed by the ground is

greater if the apple bounces

Whether a truck comes to a stop by crashing into a brick wall or a haystack, the stopping force is

greater with the brick wall

A clerk can lift containers a vertical distance of 1 m, or roll them up a 2-m-long ramp to the same elevation. With the ramp, the applied force needed is

half as much.

the speed of a bullet fired from a gun will be about the same as the speed of the recoiling gun

if the masses of the bullet and gun are equal

A cannonball fired from a long-barrel cannon will have a greater muzzle velocity because the cannonball receives a greater

impulse

the change in momentum of an object is equal to the

impulse that acts on it

compared with falling on a wood floor, a wine glass may not break when it falls on a carpeted floor because of

longer time to stop

When a cannon fires a cannonball at a given speed, the smaller recoil speed of the cannon is due to different

masses

An iron ball and wooden ball of the same size are dropped simultaneously from a tower and reach the ground at the same time. The iron ball has a greater

momentum

a heavy truck and a small truck roll down a hill. neglecting friction, at the bottom of the hill the heavy truck has greater

momentum

an object in motion is an object that has

momentum

a fan attached to an ice sail craft stalled on a windless day blows air into the sail that bounces backward upon impact. the boat

moves in the direction of the wind impact force

An object that has kinetic energy must be

moving

According to the impulse-momentum relationship Ft = change in mv, a falling baseball hits a player with a force of F. the t in the equation is the time

of contact of the ball hitting the player

Work is done by gravity on a bowling ball that rolls

on a sloped surface.

If you push for an hour against a stationary wall, you do no work

on the wall

Consider a gun with a pellet that is more massive than the gun. The firing speed is greater for the

recoiling gun

it is correct to say that impulse is equal to

the change in momentum

To catch a fast-moving softball with your bare hand, you extend your hand forward just before the catch and then let the ball ride backward with your hand. Doing this reduces the catching force because the

time of the catch is increased

the distinction between impulse and force involves the

time the force acts

If you push an object twice as far while applying the same force, you do

twice as much work

When you push an object a certain distance while applying twice the force, you do

twice as much work

A 1000-kg car and a 2000-kg car are hoisted the same vertical distance in a service station. Raising the more massive car requires

twice as much work.

An object lifted 10 m gains a certain amount of potential energy. If it is lifted 20 m, its gain in potential energy is

twice as much.

When you ride your scooter you have momentum. When you ride twice as fast you have

twice the momentum

recoil is noticeable if we throw a heavy ball while standing on a skateboard. if instead we go through the throwing motion but hold onto the ball, without friction effects our net recoil will be

zero


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