lesson #12

Lesson #12
E.Q: How impulse and momentum are related

key points
each slide

Multiple Choice

Momentum is equal to

• one half mass times velocity squared

• mass

• mass times velocity

• mass divided by velocity

Multiple Choice

Which object has more momentum?

• Baseball in the pitchers hand

• baseball, lost, in a messy room

• baseball in flight

• baseball in a catchers mitt

Multiple Choice

momentum is a

• vector

• scalar

• force

CONSERVATION OF MOMENTUM

• 2nd big conservation law in Physics (after Conservation of Energy)

• The total momentum of a system of objects remains constant.

• Very useful in observing collisions and explosions.

Multiple Choice

A 0.250 kg cart moving at 0.400 m/s has how much momentum?

• 0.1 kg-m/s

• 1 kg-m/s

• 10 kg-m/s

• 100 kg-m/s

Multiple Choice

Does a student standing still have momentum?

• yes

• no

Multiple Choice

The units for Impulse are

• kg

• $$N\cdot s$$ or J

• N

• m/s or J

Multiple Choice

The impulse is ______ the change in momentum

• greater than
• equal to
• less than
• always double

Multiple Choice

During a collision. an object experiences an impulse. How can this impulse be calculated?

• Multiplying force by time

• Multiplying mass by velocity

• Dividing velocity by time

• Multiplying mass by acceleration

Multiple Choice

A 10,000 kg train is moving at 20 m/s. What is its momentum?

• 500

• 10,0000

• 200,000

• 2,000,000

Momentum Summary

• momentum is mass times velocity, indication of how hard it is to stop an object

• Impulse is force times time; Impulse is also equal to change in momentum.

• Individual objects change momentum any time there is a net force, but the total amount of momentum does not change.

• Momentum and Impulse will be useful in analyzing collision problems

lesson#12 part 2

WORK in Class momentum-impluse

1. A 0.5 kg ball is moving east at a speed of 2 m/s. Calculate the momentum of the ball.

2. A shopping cart with a mass of 10 kg is pushed and reaches a speed of 1.5 m/s in 2 seconds. If the applied force is constant, what is the impulse delivered to the cart?

continuation..

3. A 0.8 kg ball is suspended from a string. A 0.05 kg projectile hits it horizontally at a speed of 400 m/s and becomes embedded in the ball. Calculate the impulse imparted to the ball and the final momentum of the ball-projectile system.
4. Two skaters, one of 50 kg and another of 60 kg, are standing on ice and push each other. If the 50 kg skater moves backward at 2 m/s, at what speed will the 60 kg skater move?

continuation..

5. A 1500 kg car is parked and is hit by another car of 1000 kg moving at 10 m/s. If after the collision they move together, at what speed will they do so?
6. A 2000 kg railway wagon moving at 4 m/s collides and couples with another wagon of 3000 kg which is initially at rest. Find the speed of the combined wagons after the collision.