How It Works

InstaEDU makes it easy to find a great tutor and connect instantly

  • Connect with the perfect tutor, anytime 24/7

    Never get stuck on homework again. InstaEDU has awesome tutors instantly available around the clock.

  • Work together with the best lesson tools

    Our lesson space lets you use video, audio or text. Upload any assignment and work through it together.

  • Try it free—then lock in a super low rate

    Anyone can try InstaEDU for up to 2 hours for free. After that, rates start at just 40¢/minute.

Basic Physics Questions:

Part A A Mack truck and a small Volkswagen collide head-on. Which of…

Complete Question Text:

Part A
A Mack truck and a small Volkswagen collide head-on. Which of the following statements is true about the collision?

The force the Volkswagen exerts on the truck is equal to the force the truck exerts on the Volkswagen.

The force the Volkswagen exerts on the truck is greater than the force the truck exerts on the Volkswagen.

The force the Volkswagen exerts on the truck is smaller than the force the truck exerts on the Volkswagen.
SubmitHintsMy AnswersGive UpReview Part
Part B
A truck rear-ends a car that is initially stationary. The truck weighs ten times more than the car. Which statement is true about the collision?

The magnitude of the acceleration of the car is equal to the magnitude of the acceleration of the truck.

The magnitude of the acceleration of the car is ten times greater than the magnitude of the acceleration of the truck.

The force exerted onto the car is ten times greater than the force exerted onto the truck.
SubmitHintsMy AnswersGive UpReview Part
Part C
A glass that falls onto a carpeted floor has less chance of breaking than a glass that falls (from the same height) onto a wooden floor. Why?

The glass that falls onto the carpet has a smaller impulse in stopping.

The glass that falls onto the carpet takes a longer time to stop.

The glass that falls onto the carpet has a smaller change in momentum in stopping.
SubmitHintsMy AnswersGive UpReview Part
Part D
A stationary 100-kg person is initially holding a 50-kg ball while standing on a skateboard. The person throws the ball to the right, and the ball moves (with respect to the ground) with a speed of 12 m/s. The person on the skateboard ____________.

moves to the left with a speed of 12 m/s

moves to the left with a speed of 4 m/s

remains stationary

moves to the left with a speed of 6 m/s
SubmitHintsMy AnswersGive UpReview Part
Part E
Consider two carts, initially at rest. Cart 1 is twice as massive as cart 2. If you push on cart 1 for 3 seconds and then push on cart 2 with the same force for 3 seconds, how do the final momenta of the two carts compare? (Ignore the effect of friction.)

The momentum of cart 1 is twice as high as that of cart 2.

The momenta of the two carts are equal.

The momentum of cart 2 is twice as high as that of cart 1.
SubmitHintsMy AnswersGive UpReview Part
Part F
Consider two carts, initially at rest. Cart 1 is twice as massive as cart 2. If you push on cart 1 for 3 seconds and then push on cart 2 with the same force for 3 seconds, how do the final speeds of the two carts compare? (Ignore the effect of friction.)

The speed of cart 1 is twice as great as that of cart 2.

The speed of cart 2 is twice as great as that of cart 1.

The speeds of the two carts are equal.
SubmitHintsMy AnswersGive UpReview Part
Part G
A 200-lb person pushes on the back of a 100-lb person. Both people are on skateboards and are initially stationary. After the push, the 200-lb person is moving to the right with a speed of 4 m/s. The 100-lb person is ________.

stationary

moving to the left with a speed of 2 m/s

moving to the left with a speed of 8 m/s

moving to the left with a speed of 4 m/s
SubmitHintsMy AnswersGive UpReview Part
Part H
A car is driving down the highway with an initial speed of 30 m/s. It slams into the back of an identical car (same mass), which was initially going only 10 m/s (in the same direction as the faster car). If the collision is perfectly inelastic, the final speed of the two cars is ________.

30 m/s

40 m/s

20 m/s

15 m/s
A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.

it drifts toward a distant port

its speed is greater than the speed of the car

its mass is greater than the mass of the car

its mass times velocity is greater than that of the car
How is Dr. Hewitt able to break a piece of wood in his demonstration?

He moves his hand very quickly.

He uses a heavy object to break the piece of wood.

He moves his hand very slowly.
SubmitHintsMy AnswersGive UpReview Part
Part B
How does Dr. Hewitt break the piece of wood?

He exerts a large force to break the wood.

He creates a change in momentum of his hand over a long period of time.

He causes a change in momentum of his hand over a short period of time.

He causes a change in momentum over a long period of time.
SubmitHintsMy AnswersGive UpReview Part
Part C
What would Dr. Hewitt need to have done to exert an even greater force than he did in his karate demonstration?

Increase the change in momentum, and increase the time duration.

Decrease the change in momentum, and increase the time duration.

Increase the change in momentum, and decrease the time duration.

Decrease the change in momentum. and increase the time duration.
Follow through is important in golf because it results in a greater _______.

force on the ball

impulse on the ball

force and greater impulse on the ball

swinging motion
A boxer rides with the punch so as to reduce _______.

impulse

momentum

speed

force

When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______.

greater than the momentum of the fired cannonball

equal and opposite to the momentum of the fired cannonball

less than the momentum of the fired cannonball

the same as that of the fired cannonball
When two vehicles collide, momentum is conserved _______.

only if deformation of either vehicle doesn't occur

if the collision is inelastic

if the collision is elastic

whether the collision is elastic or inelastic
When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.

remains the same

decreases

converts to spurious motion

increases
Suppose we repeat the experiment from the video, but this time we use a rocket three times as massive as the one in the video, and in place of water we use a fluid that is twice as massive (dense) as water. If the new fluid leaves the rocket at the same speed as the water in the video, what will be the ratio of the horizontal speed of our rocket to the horizontal speed of the rocket in the video after all the fluid has left the rocket? (Ignore air resistance.)

1

3/2

1/3

1/2

2/3
A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

force against the rifle is smaller than against the bullet.

rifle has much more mass than the bullet.

momentum is mainly concentrated in the bullet.

momentum of the rifle is smaller.
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

time of impact is decreased.

relative velocity is less.

time of impact is increased.

force of impact is reduced.

none of these
A car traveling along the highway needs a certain amount of force exerted on it to stop it in a certain distance. More stopping force is required when the car has

more mass.

less stopping distance.

more momentum.

all of these

none of these

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has

increased time of impact.

increased momentum.

decreased time of impact.

decreased impulse.

Compared to falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the
Compared to falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the

carpet provides a smaller impulse and a longer time.

stopping time is longer on the carpet.

carpeted floor provides a smaller impulse.

stopping time is shorter on the carpet.
The force that accelerates a rocket in outer space is exerted on the rocket by the

exhaust gases.

rocket's nose cone.

atmospheric pressure.

rocket's wings.

none of these

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?

half the sum of their original momentums

twice the sum of their original momentums

0

impossible to determine without additional information

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 this lunch is

6/5 m/s.

1/2 m/s.

5/6 m/s.

1 m/s.

2/5 m/s.

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

not move by this wind impact.

then move in the direction of the wind impact force.

then move, but in the opposite direction of the wind impact force.
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?

the bug

your car

both the same
A 5000-kg freight car moving at 2 m/s runs into a 10,000-kg freight car at rest. They couple upon collision and move away as one body at

2 m/s.

1/3 m/s.

1 m/s.

2/3 m/s.

Show more
Asked on Feb. 25, 2014, 4:14 a.m.
Peter L. Tutors Basic Physics + 16 others
Harvard University 2016 - Physics and Math
26
"I am currently an undergraduate tutor at Harvard University that specializes in Math and Physics. In the past, I have worked..."

Part A
A) The force the Volkswagen exerts on the truck is equal to the force the truck exerts on the Volkswagen.

This is simply Newton's third law.

Part B
B) The magnitude of the acceleration of the car is ten times greater than the magnitude of the acceleration of the truck.

Since the force is the same, the acceleration is just a = F/m.

Part C
B) The glass that falls onto the carpet takes a longer time to stop.

Even though the impulse is the same in both cases, the carpet takes longer so the force is less.

Part D
D) moves to the left with a speed of 6 m/s

This is just conservation of momentum.

Part E
B) The momenta of the two carts are equal.

Impulse is just a change in momentum.

Part F
B) The speed of cart 2 is twice as great as that of cart 1.

They have the same momentum, so the lighter cart will be faster.

Part G
C) moving to the left with a speed of 8 m/s

This is conservation of momentum.

Part H
C) 20 m/s

This is conservation of momentum.

A slowly moving ship can have a greater momentum than a fast-moving racing car when _______.

C) its mass is greater than the mass of the car

This is just the definition of momentum p = mv.

How is Dr. Hewitt able to break a piece of wood in his demonstration?

A) He moves his hand very quickly.

He imparts a large impulse by moving quickly.

Part B
C) He causes a change in momentum of his hand over a short period of time.

He moves his hand quickly, and so the momentum changes over a short time.

Part C

C) Increase the change in momentum, and decrease the time duration.

Since I = Ft, this follows.

Follow through is important in golf because it results in a greater _______.

B) impulse on the ball

You apply the force over a longer time and produce a greater impulse.

A boxer rides with the punch so as to reduce _______.

D) force

A longer time means less force for the same impulse.

When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______.

B) equal and opposite to the momentum of the fired cannonball

This is conservation of momentum.

When two vehicles collide, momentum is conserved _______.

D) whether the collision is elastic or inelastic

Momentum is always conserved.

When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______.

A) remains the same

Momentum is always conserved.

Suppose we repeat the experiment from the video, but this time we use a rocket three times as massive as the one in the video, and in place of water we use a fluid that is twice as massive (dense) as water. If the new fluid leaves the rocket at the same speed as the water in the video, what will be the ratio of the horizontal speed of our rocket to the horizontal speed of the rocket in the video after all the fluid has left the rocket? (Ignore air resistance.)

E) 2/3

The rocket gains 2x the momentum, but it is 3x heavier.

A rifle recoils while firing a bullet. The speed of the rifle's recoil is small because the

B) rifle has much more mass than the bullet.

With the same momentum, the rifle has more mass, so it moves with smaller velocity.

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

C) time of impact is increased.

The impulse is I = Ft, so an increased time means less force.

A car traveling along the highway needs a certain amount of force exerted on it to stop it in a certain distance. More stopping force is required when the car has

D) all of these

In all cases, more force is required for increased momentum and energy change.

Padded dashboards in cars are safer in an accident than nonpadded ones because an occupant hitting the dash has

A) increased time of impact.

Increased time means less force.

Compared to falling on a stone floor, a wine glass may not break when it falls on a carpeted floor because the

B) stopping time is longer on the carpet.

Longer time means less force.

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

A) exhaust gases.

The gases exert an impulse on the rocket.

Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet?

C) 0

Their momenta are equal and opposite, so 0.

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 this lunch is

C) 5/6 m/s.

This is conservation of momentum.

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

B) then move in the direction of the wind impact force.

The sailcraft moves in the direction of the force.

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?

C) both the same

This is conservation of momentum.

A 5000-kg freight car moving at 2 m/s runs into a 10,000-kg freight car at rest. They couple upon collision and move away as one body at

D) 2/3 m/s.

This is from conservation of momentum.

The student's feedback

Need more help?

          By sending a message, you agree to our Terms of Service.

          644 Basic Physics tutors are available online to help.

          Browse Tutors

          See how InstaEDU works: