Physics 1-3-08

Introduction of momentum

What will be done the next two weeks

• We will be discussing the concept of Momentum until Wednesday of next week

• Next Thursday/Friday will be spent on review for test

• Find your old tests, use as a basis for studying.

New Year New Books (almost)

• We have new books, but are one short

• If somebody is absent, or If I have 2 that really want to share

• Have asked for another book…

Those getting books

• Enter book #, (if it has not already been done)

• Write name and year in front

• Sign list, for teacher

Question

• What would you rather get hit with?

• A bowling Ball or a steel ball bearing?

On what does your answer Depend?

Momentum

• Multiply the two factors together and you can begin to quantify the risk in being hit by the object

• The name of the value is called momentum

Momentum

• “Pain upon impact”• “Inertia in motion”• Quantity of motion found by multiplying an

objects mass by its velocity• It is a vector value (Magnitude and

Direction)• Units Kg m/s

What does not have momentum?

What has more momentum?

• The statue of liberty or a SUV moving at 60 mph done the road?

How can one change momentum?

• Examples of objects changing their momentum

Impulse

• The measure of a change in momentum

• Any change in momentum requires a net force

• Any application of a net force, results in a change of momentum of the object

What is Newton’s second law?

To find the impulse of an object

• Fnet Δt = m Δ v = impulse

Car Crashes

• Why do some people survive and others do not?

Important

• For a given crash, the impulse is constant regardless of how the crash occurs

• Impulse = mΔv

Time and force

• The length of time it takes for the crash to be complete determines the amount of force applied during the crash

• Seat belts• Foam padding• Air Bags• Crumple zones

Change of momentum and Sports

• Baseball/ softball•

Golf

Homework

• New Book!

• Page 233

• Problems 1-5