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1-5

How do you calculate the momentum of an object?

1-5A

How do you calculate the momentum of an object?

Momentum = Mass x VelocityMomentum = Mass x Velocity

1-10

True or False?

Momentum is a vector quantity.

1-10A

True or False?

Momentum is a vector quantity.

True

1-15What is the momentum of a 0.520-kg object moving at a velocity of 14 m/s?

1-15AWhat is the momentum of a 0.520-kg object moving at a velocity of 14 m/s?

Momentum = Mass x Velocity

p = mv = (0.520 kg)(14 m/s)

p = 7.28 kg m/s

1-20

A) a .22-caliber bullet fired from a rifleB) a bus speeding along a highway

Which of the following objects has the greatest Momentum?

B) a bus speeding along a highwayC) a sprinter running the 100-yard dashD) the Earth in its orbitE) not enough info to answer

1-20A

A) a .22-caliber bullet fired from a rifleB) a bus speeding along a highway

Which of the following objects has the greatest Momentum?

B) a bus speeding along a highwayC) a sprinter running the 100-yard dashD) the Earth in its orbitE) not enough info to answer

1-25What is the total momentum of the following situation? Assume there is no friction.

2 kg1.5 m/s 0.8 m/s

3 kg

1-25AWhat is the total momentum of the following situation? Assume there is no friction.

2 kg1.5 m/s 0.8 m/s

3 kg

Momentum of LH-cart = (2 kg)(1.5 m/s) = + 3 kg m/s

Momentum of RH-cart = (3 kg)(- 0.8 m/s) = - 2.4 kg m /s

Total Momentum = + 3 kg m/s – 2.4 kg m/s

= 0.6 kg m/s

2-5An impulse is equal to which of the following?

A) force times distanceB) force of impactB) force of impactC) change in kinetic energyD) change in momentumE) none of these

2-5AAn impulse is equal to which of the following?

A) force times distanceB) force of impactB) force of impactC) change in kinetic energyD) change in momentumE) none of these

2-10If a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact?

2-10AIf a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact?

Increase the time of impact

2-15What is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds?

2-15AWhat is the change in momentum of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds?

Change in momentum = impulse = F tChange in momentum = impulse = F t

F t = (75 N)(0.18 s)

F t = 13.5 N s

2-20A Mack truck and bug are traveling towards one another when they collide head-on. Which one experiences the greater impulse?

A) the Mack truckA) the Mack truckB) the bugC) they both experience the same impulseD) not enough info

2-20AA Mack truck and bug are traveling towards one another when they collide head-on. Which one experiences the greater impulse?

A) the Mack truckA) the Mack truckB) the bugC) they both experience the same impulseD) not enough info

2-25A 1,000 kg rocket is launched from rest to a speed of 2500 m/s in a time of 2.5 minutes. What was the average force (in Newtons) exerted on the rocket?

2-25AA 1,000 kg rocket is launched from rest to a speed of 2500 m/s in a time of 2.5 minutes. What was the average force (in Newtons) exerted on the rocket?

Change in momentum = ImpulseChange in momentum = Impulse

∆m v = F t ==> F = m (vf – vi) / t

F = (1000 kg)(2500 m/s - 0 m/s )/(150 s)

F = 16,667 N

3-5

True or False?

Momentum is conserved in all kinds of collisions. all kinds of collisions.

3-5A

True or False?

Momentum is conserved in all kinds of collisions. all kinds of collisions.

True

3-10Which kind of collision conserves both momentum and kinetic energy?

A) elasticB) inelasticB) inelasticC) bothD) neither

3-10AWhich kind of collision conserves both momentum and kinetic energy?

A) elasticB) inelasticB) inelasticC) bothD) neither

3-15Why is it safer to stop an out-of-control car by running into a pond versus hitting a concrete wall?

3-15AWhy is it safer to stop an out-of-control car by running into a pond versus hitting a concrete wall?

By running into the pond, the time it By running into the pond, the time it takes the car to slow down to a stop is lengthened. Therefore the stopping force is decreased.

3-20Why is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)?

3-20AWhy is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)?

A bouncing collision is more damagingA bouncing collision is more damagingbecause the change in velocity, andtherefore the change in momentum, isgreater. This leads to a larger force.

3-25A 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is 0.078 sec, what was the force of impact?

3-25AA 0.25 kg ball is hit by a stick - the incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is 0.078 sec, what was the force of impact?

Impulse = Change in Momentum

F t = m v ==> F = m (vf – vi) / t

F = (0.25 kg)(-20 m/s - 25 m/s)/(0.078 s)

F = -144.2 N

4-5When an asteroid collides with the Moon, the Moon drastically changesthe momentum of the asteroid. Byhow much does the Moon change itsmomentum?momentum?

4-5AWhen an asteroid collides with the Moon, the Moon drastically changesthe momentum of the asteroid. Byhow much does the Moon change itsmomentum?momentum?

Precisely the same amount

4-10A firecracker is sitting on the ground when it is lit. After the explosion, what is the total momentum of the pieces flying away?

4-10AA firecracker is sitting on the ground when it is lit. After the explosion, what is the total momentum of the pieces flying away?

Zero!!!Zero!!!

…because the momentum of the firecracker before the explosion was zero, and momentum must be conserved.

4-15A bullet is fired from a heavy rifle.

Two questions:

Which one experiences a greater change in momentum?change in momentum?

Which one experiences a greater change in velocity?

4-15AA bullet is fired from a heavy rifle.

Two questions:

Which one experiences a greater change in momentum?change in momentum?

Which one experiences a greater change in velocity?

NIETHER!!! They are the same.

The Bullet.

4-20Two billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision?

Bonk!

#1 #1

#2 A B C

4-20ATwo billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision?

Bonk!

#1 #1

A B C#2

4-25

Type Question Here

Momentum of LH-cart = (3 kg)(2.5 m/s) = +7.5 kg m/s

Momentum of RH-cart = (2 kg)(-1.8 m/s) = -3.6 kg m/s

4-25A

3 kg2.5 m/s 1.8 m/s

2 kg

Momentum of RH-cart = (2 kg)(-1.8 /s) = -3.6 /s

Total Momentum = +3.9 kg m/s

After collision ==> 3.9 kg m/s = (5 kg)v

v = (3.9 kg m/s)/(5 kg) = +0.78 m/s

5-5How many triangles are there in this figure?

5-5A

3535

5-10Name the actor and movie that produced this famous quote:

“Boards don’t hit back.”

5-10A

Bruce Lee, inBruce Lee, inEnter the Dragon

5-15The word “Hamster” means what in German?

A) Bacon MixB) HoarderC) RodentD) Nocturnal

5-15AThe word “Hamster” means what in German?

A) Bacon MixB) HoarderC) RodentD) Nocturnal

5-20

As of early 2008, what is the smallest commercial car in the United States?

5-20AThe Smart Car

What California gold-rush entrepreneur used his knowledge of bouncing collisions to design a nearly 90% efficient water wheel?nearly 90% efficient water wheel?

5-25ALester A. Pelton,inventor of the Pelton water wheel

Daily Double

Two carts collide and stick together as shown above. What is the velocity of the carts after

3 kg2.5 m/s 1.8 m/s

2 kg

above. What is the velocity of the carts after they’ve collided? Assume there is no friction.