Hopefully we have seen the value of

Newtonian physics,

But also we note that they aren't the best

tool for every problem.

Now let us move into conservation laws.

As we begin we need to place this information

somewhere we have been.

So we can make an association with what we have

learned.

Momentum and its relation to force

By definition linear momentum is the mass times

the velocity.

UNITS

This is saying that if I have net force

acting on an object for a period of time

then it will have a change in momentum.

Lets solve this equation for momentum.

What is momentum?

(not just inertia)

Momentum can be thought

of as 'moving' inertia

Review

Think inertia

Think 2 thing

1 Think mass

2 Motion and force (f=ma)

How much Momentum does a 100 kg

bear have moving at 8 m/s?

A. 200 kg(m/s)

B. 400 kg(m/s)

C. 600 kg(m/s)

D. 800 kg(m/s)

How much momentum does it lose

if it slows down to 2 m/s?

For my bear problem, something happened to slow the bear down.

Just like matter it can't just disappear.

This says that some force acting

in a given amount of time, will change

my momentum.

consider a

tennis ball

and racket

When the ball first hits the racket

not a lot of force happens

then it grows, and starts to move away

and the force shrinks

this force looks like this:

This force happening over a period of time is special.

We call it an impulse

impulse-momentum theorem

**# 5, what value of F_max gives an impulse of 6.0 N*s?**

Meaning that whatever we begin with

will be constant through out the whole

motion.

Let us start with momentum

**#11 Far in space where gravity is negligible, a 425 kg rocket traveling at 75 m/s fires its engines. This picture shows the thrust force as a function of time. The mass lost by the rocket during these 30 s is negligible.**

a. What impulse does the engine impart to the rocket?

b. At what time does the rocket reach its maximum speed? What is that speed?

a. What impulse does the engine impart to the rocket?

b. At what time does the rocket reach its maximum speed? What is that speed?

**A pitcher throws a .15 kg baseball with a speed of 35 m/s to a batter.**

a. If the ball is hit straight back to the pitcher with a speed of 55 m/s, what was the impulse given to the ball?

b. If the impact time was 2.5 ms, what was the average force delivered to the ball?

a. If the ball is hit straight back to the pitcher with a speed of 55 m/s, what was the impulse given to the ball?

b. If the impact time was 2.5 ms, what was the average force delivered to the ball?

**1500 N**

**15,000 N s**

**30 s**

110 m/s

110 m/s

**13.5 N s**

**5400 N**

**A golfer is able to deliver 1500 N of force for a time of 4.0 ms to a 75 g golf ball. What is the speed just after the impact?**

**80 m/s**

"Why is stop and think 9.1, F?"

"Can you go over drawing a before and after pictorial representation?"

"I didn't understand how and why we are using integrals in some formulas.. can we review them?"

"can you explain impulse and the momentum theorem?"

"Can you explain how inertia is related to momentum?"