10/21/10
Post date: Oct 21, 2010 3:51:21 PM
Bell Ringer: What is momentum?
9.1 Notes (PowerPoint)
Introduction to Momentum
If you are going to be hit by a ball...
Would you prefer it to move fast or slow?
Would you prefer a baseball or a bowling ball?
Momentum is a measure of how much tendency an object has to keep its motion
Momentum depends on the velocity of the object and it's mass
Equation for momentum: p = mv, or momentum = mass times velocity
Unit for momentum is kg*m/s, read "kilogram meter per second"
Example: The momentum of an 80 kg biker moving at 5 m/s is (80kg)*(5m/s) = 400 kg*m/s
Practice: Page 178, problem 1
p = mv practice problems on overhead (may also be found in "handouts" section of this web site)
Impulse-Momentum theorem
If a constant force is applied to something over a period of time, we call the product of force and time the impulse
If the mass of an object is constant, then the impulse is equal to the change in momentum of the object
Equation: Force x time = change in momentum or Force x time = mass x change in velocity
See page 177 for the symbols in this equation
Example: A baseball being hit by a bat (page 178)
Application question: Why are we taught to follow through when we swing a bat?
Practice: Page 178, problem 2-4