Momentum Concept Review

• There will be 60 seconds to answer each question from the time I am done reading unless otherwise noted.

• Correct answers will earn the points denoted by the question. Incorrect answers will not be penalized.

• Mr. Richter has absolute power to give points or take them away as he sees fit.

• At Final Jeopardy, each time may wager all of their earned points, or $2000, whichever is greater.

• The winning team will earn 2 points of extra credit each on tomorrow’s test. The second place team will earn 1 point.

Momentum!Momentum and Impulse

Conservation of Momentum

Collisions Calculations Potpourri

Q $100

Q $200

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Q $500

Q $100 Q $100Q $100 Q $100

Q $200 Q $200 Q $200 Q $200

Q $300 Q $300 Q $300 Q $300

Q $400 Q $400 Q $400 Q $400

Q $500 Q $500 Q $500 Q $500

Final Jeopardy: Calculations

$100 Question from Momentum and Impulse

• The momentum of an object is determined by what two factors?

$100 Answer from Momentum and Impulse

• Mass and velocity

$200 Question from Momentum and Impulse

• What are the units of impulse?

$200 Answer from Momentum and Impulse

• kg m/s (same as momentum, change in momentum)

$300 Question from Momentum and Impulse

• What two factors contribute to the magnitude of the change in momentum of an object?

$300 Answer from Momentum and Impulse

• Force and time.

$400 Question from Momentum and Impulse

• Using the concept of impulse, explain why we use airbags.

$400 Answer from Momentum and Impulse

• Can accomplish the same change in momentum by applying a smaller force for a larger amount of time.

$500 Question from Momentum and Impulse

• Can a golf ball have the same momentum as a bowling ball? If so, how? If not, why not?

$500 Answer from Momentum and Impulse

• Yes, it just needs a higher velocity.

$100 Question from Conservation of Momentum

• Momentum is always conserved in the absence of ________.

$100 Answer from Conservation of Momentum

• Friction

$200 Question from Conservation of Momentum

• When a bullet is fired from a gun, the gun moves backward. Is the velocity of the gun greater than, equal to, or less than the velocity of the bullet? Why?

$200 Answer from Conservation of Momentum

• Velocity is less because the gun has more mass.

$300 Question from Conservation of Momentum

• Before a collision, Object A has 20 kg m/s of momentum. Object B is at rest. After the collision, Object A has 12 kg m/s of momentum. How much momentum does object B have?

$300 Answer from Conservation of Momentum

• 8 kg m/s

$400 Question from Conservation of Momentum

• The Law of Conservation of Momentum arises from when two objects are in contact with one another, they push with the same force for the same amount of time. This is a derivation from what previously discussed concept in physics.

$400 Answer from Conservation of Momentum

• Newton’s Third Law

$500 Question from Conservation of Momentum

• A man and an elephant standing on skateboards push off of each other. The magnitude of the man’s momentum is:

A. less than that of the elephant

B. equal to that of the elephant

C. more than that of the elephant

D. need more information

$500 Answer from Conservation of Momentum

• B. Equal to that of the elephant.

$100 Question from Collisions

• In which type or types of collision is momentum conserved?

$100 Answer from Collisions

• All types (elastic and inelastic)

$200 Question from Collisions

• In which type or types of collision is kinetic energy NOT conserved?

$200 Answer from Collisions

• Kinetic energy is not conserved in inelastic collisions.

$300 Question from Collisions

• When energy is “lost” in a collision, it is primarily converted into what form?

$300 Answer from Collisions

• Internal energy (the energy when objects deform)

$400 Question from Collisions

• Give an example of a perfectly inelastic collision.

$400 Answer from Collisions

• Answers will vary: something like a receiver catching a football.

$500 Question from Collisions

• Why do objects experience a greater force in elastic collisions as opposed to inelastic collisions?

$500 Answer from Collisions

• In elastic collisions, objects experience a greater change in momentum, and therefore a greater force.

$100 Question from Calculations

• Calculate the momentum of a 0.15 kg baseball traveling at 24 m/s.

$100 Answer from Calculations

• 3.6 kg m/s

$200 Question from Calculations

• If an engine supplies a force of 1200 N, how much time is required to accelerate an 800 kg car from rest to 18 m/s?

$200 Answer from Calculations

• 12 seconds

$300 Question from Calculations

• An 85 kg astronaut floating in space pushes a 30 kg asteroid that is floating nearby. If the asteroid moves to the right at 4.4 m/s after the push, what is the astronaut’s velocity?

$300 Answer from Calculations

• -1.6 m/s (1.6 m/s to the left)

$400 Question from Calculations

• A dry cleaner throws a 22 kg bag of laundry onto a stationary 9.0 kg cart. The cart and laundry bag begin moving at 3.0 m/s to the right. Find the velocity of the laundry bag before the collision.

$400 Answer from Calculations

• 4.2 m/s to the right

$500 Question from Calculations

• A 10 kg bowling ball traveling at 12 m/s collides with a 1.5 kg bowling pin initially at rest. After the collision, the bowling ball continues in the same direction at a speed of 8.0 m/s. What is the velocity of the pin after the collision?

$500 Answer from Calculations

• 27 m/s

$100 Question from Potpourri

• Is a basketball more likely to have mostly elastic collisions or mostly inelastic collisions?

$100 Answer from Potpourri

• Mostly elastic collisions.

$200 Question from Potpourri

• When a ball is dropped and then bounces, what is the evidence to show that kinetic energy is not entirely conserved?

$200 Answer from Potpourri

• The ball will not bounce up to as high as its original height.

$300 Question from Potpourri

• When trying to catch a water balloon, which type of collision should one attempt to have if one wants the water balloon to survive?

$300 Answer from Potpourri

• Inelastic.

$400 Question from Potpourri

• A student knows the initial and final velocities of two objects before and after a collision, as well as their masses. How could he use this information to determine whether the collision as elastic or inelastic.

$400 Answer from Potpourri

• Compare the total kinetic energy before the collision to the total kinetic energy after the collision. If they are equal, the collision was elastic.

$500 Question from Potpourri

• An astronaut carrying a camera in space finds herself drifting away from a space shuttle after her tether breaks. If she has no propulsion device, what should she do to move back to the shuttle?

$500 Answer from Potpourri

• Throw the camera in a direction away from the shuttle.

Final Jeopardy:• During practice, a student kicks a 0.40 kg

soccer ball with a velocity of 8.5 m/s into a 0.15 kg bucket lying on its side. The bucket travels with the ball after the collision.

1. What is the final velocity of the combined mass?

2. What is the decrease in kinetic energy during the collision?

Final Jeopardy Answer

1. 6.2 m/s

2. 3.9 J