AP Physics 1 : Impulse and Momentum

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #21 : Impulse And Momentum

A train of mass  traveling at strikes a car stuck on the tracks of mass . The car becomes stuck on the train.

 

Determine the final velocity of the train.

Possible Answers:

None of these

Correct answer:

Explanation:

We will need to use conservation of momentum to solve this problem.

 

 

Where  and  refer to the train, and  and  refer to the car. and  refer to the final state of both the train and the car.

 

Rearranging using algebra......

 

 

 

Plugging in our values, we get .

Example Question #22 : Impulse And Momentum

A train of mass  traveling at strikes a car stuck on the tracks of mass . The car becomes stuck on the train.

 

Determine the final velocity of the car.

Possible Answers:

None of these

Correct answer:

Explanation:

We will need to use conservation of momentum to solve this problem.

 

 

Where  and  refer to the train, and  and  refer to the car. and  refer to the final state of both the train and the car.

 

Rearranging using algebra......

 

 

 

Plugging in our values, we get .

Example Question #23 : Impulse And Momentum

A train of mass  traveling at  strikes a car stuck on the tracks of mass .

 

Let's assume this collison took  to happen. That is, it took the car  to accelerate to it's new velocity. Determine the force experienced by the car.

Possible Answers:

None of these

Correct answer:

Explanation:

We will need to use conservation of momentum to solve this problem.

 

 

Where  and  refer to the train, and  and  refer to the car. and  refer to the final state of both the train and the car.

 

Rearranging using algebra......

 

 

 

Plugging in our values, we get .

 

 

 

Then, we will need to find out final momentum of the car.

 

 

 

 

 

Since our intial momentum of the car was , our change in momentum will be equal to the .

 

 

 

 

We will use the definition of impulse, which is the change in momentum:

 

 

We will use substitution:

 

 

Plugging in our values, we get 

Example Question #24 : Impulse And Momentum

A car of mass  is accelerated from  to  in 2s.

Determine the average total forces on this car during this time frame.

Possible Answers:

Correct answer:

Explanation:

Determine the change in the velocity of the car:

Calculate the average acceleration:

Use the definition of force:

Example Question #25 : Impulse And Momentum

A cart is traveling at  when it launches a ball straight into the air with initial velocity .

You may ignore air resistance.

How much time will the ball take from the moment it is launched to return to it's initial height?

Possible Answers:

None of these

Correct answer:

Explanation:

First, break the airborne time into two pieces, the ascent and descent.

Ascent:

The ball will need to decelerate from to .

Use acceleration due to gravity.

Solve for

Descent:

Due to parabolic motion, the ball will have the same magnitude of velocity when it returns to it's height as when it launched, albeit in the opposite direction.

Solving for

Add the times together to get the total airtime.

Example Question #26 : Impulse And Momentum

A cart is traveling at  when it launches a ball straight into the air with initial velocity . Ignore air resistance.

How far will the cart have traveled by the time the ball returns to it's initial height?

Possible Answers:

None of these

Correct answer:

Explanation:

First, break the airborne time into two pieces, the ascent and descent.

Ascent:

The ball will need to decelerate from to .

Use acceleration due to gravity.

Solve for

Descent:

Due to parabolic motion, the ball will have the same magnitude of velocity when it returns to it's height as when it launched, albeit in the opposite direction.

Solve for

Add the times together.

Multiply the airtime by the velocity of the cart.

Example Question #21 : Impulse And Momentum

An astronaut of mass throws a shot put in space. If the shot put has a magnitude of velocity of in relation to the center of the galaxy, determine the magnitude of velocity of the astronaut in relation to the center of the galaxy.

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum:

The initial momentum can be taken as zero from our reference frame.

Plug in values:

Note: The sign of the velocity for the shot put is negative because it will be in the opposite direction as the astronaut. The question is asking for magnitude though, so we know it will be positive regardless of the direction since magnitude does not take into account the direction of motion.

Example Question #28 : Impulse And Momentum

A batter makes contact with a baseball for 0.1 seconds, exerting a constant force of 100 Newtons during the contact.

What is the ball's change in momentum as a result of the contact?

Possible Answers:

Correct answer:

Explanation:

We use the equation: 

 

Where the change in momentum is .

The force, , is  and t is the time during which the force is exerted () as given by the problem statement, we plug in to the formula:

Example Question #29 : Impulse And Momentum

A locomotive of mass traveling at couples to a motionless coach without applying the brakes. Calculate the momentum change (the impulse experienced) of the coach.

Possible Answers:

Correct answer:

Explanation:

Use conservation of momentum

Plug in values:

Solve for :

Definition of impulse:

Convert  to

Plug in values:

Example Question #30 : Impulse And Momentum

A locomotive of mass traveling at couples to a motionless coach without applying the brakes. This took . Determine the average force experienced by the coach.

Possible Answers:

Correct answer:

Explanation:

Use conservation of momentum

Plug in values:

Solve for :

Definition of impulse:

Convert  to

Plug in values:

 

Plug in values

Solve for :

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