AP Physics 1 : Impulse and Momentum

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #246 : Linear Motion And Momentum

An object travels for  with a force of . For the next , the object travels with a constant force of . What is the change in the momentum for the object in the first ?

Possible Answers:

Correct answer:

Explanation:

Therefore, to find the change in the momentum, we need to sum the force in the various time intervals. Remember, we are only interested in the first , not the entire time stated in the problem.

Example Question #247 : Linear Motion And Momentum

 truck is driving at  relative to the ground. A  rocket is launched from the roof backwards at  relative to the ground. Determine the final velocity of the truck. 

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum.

The initial momentum is the combined mass of the truck and the rocket moving together

The final momentum is made up of the momentum of the truck and the rocket, which are now moving in opposite directions

Combining equations

Plugging in values:

Solving for 

 

Example Question #248 : Linear Motion And Momentum

 man is running at . From that run, he jumps on a skateboard of mass of . Assuming no energy lost to friction, determine the final velocity of the man on the board.

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum:

The man and the skateboard are stuck together, and thus become one mass:

Plugging in values:

Solving for 

 

Example Question #241 : Linear Motion And Momentum

Two wagons are held together with a rope. Lodged between them, is a very powerful spring. The rope is suddenly cut, allowing the spring to launch the wagons. If the first wagon has a mass of , and obtains a maximum velocity of , determine the momentum of the second cart. The second cart has a mass of .

Possible Answers:

 in the same direction of the first cart

 in the opposite direction of the first cart

None of these

 in the same direction of the first cart

 in the opposite direction of the first cart

Correct answer:

 in the opposite direction of the first cart

Explanation:

Using conservation of momentum.

Since nothing is moving, the initial momentum is zero

The final momentum is made up of the momentum of the two carts

Combining equations

Plugging in values:

Solving for 

The negative sign symbolizes that it will move in the opposite direction of the first cart.

 

Example Question #250 : Linear Motion And Momentum

Two wagons are held together with a rope. Lodged between them, is a very powerful spring. The rope is suddenly cut, allowing the spring to launch the wagons. If the first wagon has a mass of , and obtains a maximum velocity of , determine the momentum of the second cart. The second cart has a mass of .

Possible Answers:

 in the opposite direction

 in the same direction

 in the opposite direction

 in the opposite direction

 in the same direction

Correct answer:

 in the opposite direction

Explanation:

Using conservation of momentum.

Since nothing is moving, the initial momentum is zero

The final momentum is made up of the momentum of the two carts

Combining equations

Plugging in values:

Solving for 

The negative sign symbolizes that it will move in the opposite direction of the first cart.

 

Example Question #251 : Linear Motion And Momentum

 man is running at . From that run, he jumps on a skateboard of mass of . Assuming no energy lost to friction, determine the impulse experienced by the board

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum:

The man and the skateboard are stuck together, and thus become one mass:

Plugging in values:

Solving for 

 

Definition of impulse:

Since initial momentum was zero:

Example Question #252 : Linear Motion And Momentum

Two identical rockets are placed on the back of cars. Car  has a mass twice that of car . The rockets are identically fired for , then shut off.

How do the final velocities of the cars compare?

Possible Answers:

The velocity of the heavier car will be half that of the lighter car

None of these

They will be the same

The velocity of the lighter car will be half that of the heavier car

The velocity of the lighter car will be one-fourth that of the heavier car

Correct answer:

The velocity of the heavier car will be half that of the lighter car

Explanation:

Using 

It can be seen that since both cars have the same force applied for equal amount of time, they have identical final momentums.

Using

Where  is momentum,  is mass, and  is velocity

It can be seen that if momentum is held constant, and mass is doubled, velocity will be cut in half.

Example Question #253 : Linear Motion And Momentum

Two identical rockets are placed on the back of cars. Car  has a mass twice that of car . The rockets are identically fired for , then shut off.

How do the final kinetic energies of the cars compare?

Possible Answers:

The lighter car will have four times the kinetic energy

None of these

The heavier car will have half the kinetic energy

The heavier car will have twice the kinetic energy

The heavier car will have one-fourth the kinetic energy

Correct answer:

The heavier car will have half the kinetic energy

Explanation:

Using 

It can be seen that since both cars have the same force applied for equal amount of time, they have identical final momentums.

Using

It can be seen that if momentum is held constant, and mass is doubled, then the kinetic energy of the heavier car will be half.

Example Question #254 : Linear Motion And Momentum

 man is running at . From that run, he jumps on a skateboard of mass of . Assuming no energy lost to friction, determine the impulse experienced by the board

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum:

The man and the skateboard are stuck together, and thus become one mass:

Plugging in values:

Solving for 

 

Definition of impulse:

Since initial momentum was zero:

Example Question #61 : Impulse And Momentum

 man is running at . From that run, he jumps on a resting skateboard of mass of . Assuming no energy lost to friction, determine the final velocity of the man on the board.

Possible Answers:

None of these

Correct answer:

Explanation:

Using conservation of momentum:

The man and the skateboard are stuck together, and thus become one mass:

Plugging in values:

Solving for 

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