Physics Ch. 6

Suppose that a tiny gun made of a strong but very light material fires a bullet that is more massive than the gun itself. For such a weapon a. conservation of energy would not hold b. recoil problems would be lessened c. the target would be safer than the shooter d. conservation of momentum would not hold e. both conservation of energy and momentum would not hold

c. the target would be safer than the shooter

What is the formula for impulse = change in momentum?

Ft = (delta) mv

A rifle of mass 2 kg is suspended by strings. The rifle fires a bullet of mass 0.01 kg at a speed of 200 m/s. The recoil velocity of the rifle is about a. 1 m/s b. .001 m/s c. .1 m/s d. none

a. 1 m/s

A 5-kg shark swimming at a speed of 1 m/s swallows an absent-minded 1-kg fish swimming toward it at 4 m/s. The speed of the shark after this meal is a. 1/6 m/s b. 2/3 m/s c. 1/2 m/s d. 1/5 m/s e. 3.2 m/s

a. 1/6 m/s

It is correct to say that impulse is equal to a. the change in momentum it produces b. velocity x time c. momentum d. force x distance the force acts

a. change in momentum it produces

Momentum is transferred to the ground when an apple falls on it. The momentum absorbed by the ground is a. greater than that of the apple only if the apple bounces b. negligible compared to the momentum of the apple c. greater than that of the apple in all cases d. none

a. greater than that of the apple only if the apple bounces

A karate expert executes a swift blow and breaks a cement block with her bare hand. The magnitude of the force experienced by her hand is a. identical to the force applied to the block b. less than the force applied to the cement block c. zero d. more than the force applied to the block e. impossible to predict

a. identical to the force applied to the block

The conservation o momentum is most closely related to a. newton's 3rd law b. newton's 1st law c. Newton's 4th law d. newton's 2nd law

a. newton's 3rd law

Predict what will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is negative. a. The trucks will stick together after the collision and move to the right. b. The trucks will stick together after the collision and move to the left. c. The trucks will stick together after the collision and not move.

a. the trucks will stick together after the collision and move to the left

What will happen if you increase the mass of the green truck so that it is greater than the mass of the red truck. a. the trucks will stick together after the collision and move to the right b. the trucks will stick together and not move c. the trucks will stick together and move left

a. the trucks will stick together after the collision and move to the right

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. small, but noticeable c. the same as before

a. zero

A piece of putty moving with 1 unit of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both move with a combined momentum of a. more than 1 unit b. 1 unit c. less than 1 unit d. not enough info

b. 1 unit

Which has the largest momentum relative to Earth's surface? a. a mack truck parked in a parking lot b. a picking truck speeding along a highway c. the science building on campus d. a tightrope walker crossing niagara falls e. a dog running down the street

b. a pickup truck speeding along a highway

When you jump from an elevated position you usually bend your knees upon reaching the ground. By doing this, you make the time of the impact about 10 times as great as for a stiff-legged landing. In this way the average force your body experiences is a. more than 1/10 as great b. about 1/10 as great c. about 10 times greater

b. about 1/10 as great

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has a. increased momentum b. increased time of impact c. decreased impulse e. decreased time of impact

b. increased time of impact

If a monkey floating in outer space flows his hat away, the hat and the monkey will both... a. move a short distance and then slow down b. move away from each other, but at different speeds c. move away from each other at the same speed d. come to a stop after a few minutes e. move a short distance and go faster

b. move away from each other, but at different speeds

Predict what will happen if you reduce the magnitude of the velocity of the green truck to a magnitude smaller than that of the red truck a. trucks will stick together after the collision and not move b. the trucks will stick together after the collision and move to the left c. the trucks will stick together after the collision and move to the right

b. the trucks will stick together after the collision and move to the left

When a falling firecracker explodes, the momenta of tis pieces a. illustrate a case in which momentum is not conserved b. vectorally add to equal the initial momentum of the firecracker c. are conserved only if the fragments eject in one direction d. disintegrate

b. vectorally add to equal the initial momentum of the firecracker

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet? a. 1/2 the sum of their orignal momentums b. zero c. twice the sum of their original momentums d. impossible to determine without additional info

b. zero

A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball that is initially at rest on a frictionless surface. The speed of the putty thereafter is a. 1/5 m/s b. 1/4 m/s c. 1/6 m/s d. impossible to solve

c. 1/6 m/s

A 4 kg ball has a momentum of 12 kg m/s. What is the ball's speed? a. 48 m/s b. 12 m/s c. 3 m/s d. none

c. 3 m/s

The change in momentum, in kg m/s, that occurs in 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 b. 4 c. 6 d. 8

c. 6

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. both the same

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the a. momentum of the rifle is smaller b. force against the rifle is smaller than against the bullet c. rifle has much more mass than the bullet d. momentum is mainly concentrated in the bullet

c. rifle has much more mass than the bullet

What will happen if you change the velocity of the red truck so that it has a magnitude smaller than that of the green truck but is positive. a. The trucks will stick together after the collision and not move b. the trucks will stick together after the collision and not move c. the trucks will stick together after the collision and move to the right

c. the trucks will stick together after the collision and move to the right

Predict what will happen if the red and green truck with equal mass and equal magnitude of velocity collide. a. trucks will stick together after the collision and move to the left b. trucks will stick together after the collision and move to the right c. the trucks will stick together after the collision and not move

c. the trucks will stick together after the collision and not move

A bullet is fired from a gun. The speed of the bullet will be about the same as the speed of the recoiling gun a. because velocity is conserved b. because both velocity and momentum are conserved c. because momentum is conserved d. if the mass of the bullet equals the mass of the gun e. none

d. if the mass of the bullet equals the mass of the gun

Compared to the force that brings a small car to a stop, the force required to bring a heavy truck to a stop a. is the same b. is less c. is more d. impossible to determine w/out additional info

d. impossible to determine w/out additional info

Compared to falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the a. carpet provides a smaller impulse and a longer time b. stopping time is shorter on the carpet c. carpeted floor provides a smaller impulse d. stopping time is longer on the carpet

d. stopping time is longer on the carpet

To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the a. force of impact is reduced b. time of impact is decreased c. relative velocity is less d. time of impact is increased e. none

d. time of impact is increased

A 1000-kg car moving at 10 m/s brakes to a stop in 5 s. The average braking force is a. 4000 N b. 5000 N c. 1000 N d. 3000 N e. 2000 N

e. 2000 N

A 1-N apple falls to the ground. The apple hits the ground with an impact force of about a. 2 N b. 4 N c. 1 N d. 9.8 N e. Not enough info

e. Not enough info

A large heavy truck and a small baby carriage roll down a hill. Neglecting friction, at the bottom of the hill, the baby carriage will have a greater a. acceleration b. momentum c. speed d. all of the above e. none

e. none

A sandbag is motionless in outer space. A second sandbag with 3 times the mass moving at 12 m/s collides with it. They stick together and move at a speed of a. 3 m/s b. 6 m/s c. 4 m/s d. 8 m/s e. none

e. none

What is the formula for impulse? What are its units?

impusle = Ft Units: kg•m/s

What is the formula and units for momentum?

momentum (P) = mass x velocity Units: kg•m/s

What is the formula for conservation of momentum?

mv(before) = mv (after)