6.1 Mometum and Impulsepp. 208 - 214

Mr. Richter

Agenda

Warm-Up

Collect Science Fair Notebooks.

Introduction to Momentum

Notes: Momentum Impulse Stopping Distance and Momentum Force, Time and Impulse

Objectives: We Will Be Able To…

Compare the momentum of different moving objects.

Compare the momentum of the same object moving with different velocities.

Identify examples of change in the momentum of an object.

Describe changes in momentum in terms of force and time.

Warm-Up:

If you are asked to stop a rolling boulder, what are two things you would want to know about the boulder?

Discuss at your table.

Momentum

Momentum

What does the word momentum mean in everyday life? In physics, it means something similar.

Momentum is a measure of how difficult an object would be to stop.

Momentum depends on the mass of the object and its velocity.

Momentum

Which has more momentum, a bowling ball or a golf ball?

Actually, it depends which has more speed.

Can you think of a small object that typically has a lot of momentum?

What about a big object that has very little momentum?

Calculate Momentum

A 2250 kg pickup truck has a velocity of 25 m/s to the east. What is the momentum of the truck?

p = 56000 kg*m/s

Change in Momentum

Change in Momentum

To cause a change in momentum, a force needs to be applied over a period of time.

A change in momentum is also called impulse.

Change in Momentum Calculations

A 1400 kg car moving westward with a velocity of 14 m/s collides with a utility pole and is brought to rest in 0.30 s. Find the magnitude of the force exerted on the car during the collision.

F = 70000 N to the east

Change in Momentum

A small amount of force will require a larger amount of time to change momentum. Tapping on the brakes. Using airbag.

A large force must be used if the momentum will be changed quickly. Slamming on the brakes. No airbag.

A force applied for a longer amount of time will cause a greater change in momentum. Following through, like in sports.

Momentum and Stopping Distance

The more momentum an object has, the harder it is to stop.

This means that objects with more momentum will take longer times and distances to stop.

Using the one-dimensional motion equations from Chapter 2 (p. 58), we can calculate these distances.

Momentum and Stopping Distances

A 2250 kg car traveling to the west slows down uniformly from 20.0 m/s to 5.00 m/s. How long does it take the car to decelerate if the force on the car is 8450 N to the east? How far does the car travel during the deceleration?

Δt= 4.00 s

Δx= -50.0 m (50 m to the west)

Wrap-Up: Did we meet our objectives?

Compare the momentum of different moving objects.

Compare the momentum of the same object moving with different velocities.

Identify examples of change in the momentum of an object.

Describe changes in momentum in terms of force and time.

Homework

p. 209 #1-3 Due Monday

Due Tuesday p. 211 #1, 3 p. 213 #2