Notes: Monday, February 25, 2013 Title: Momentum and Impulse EQ: Why do gymnasts use floor mats that are very thick?

Momentum Momentum = mass × velocity The letter we use to say momentum is p So another way of writing the equation p=mv A moving object can have a large momentum if it has a large mass, high speed, or both.

Applied Question When would a roller skate and a truck have the same momentum?

Impulse An impulse is a change in momentum and depends on the force applied and the length of time it acts. Or impulse = force × time Impulse = change in momentum Ft=∆mv Remember ∆ means change in

Changes in Momentum Increasing Momentum Decreasing Momentum To increase momentum the most you want to apply the greatest possible force for the longest possible time Baseball players do this by swinging as hard as possible and by following through. To decrease momentum without causing damage the best way is use less force over an extended amount of time. When padding is used collisions happen over longer time, such that the change in momentum cause less damage.

Applied Question When a dish falls, will the impulse be less if it lands on a carpet than if it lands on a hard floor?

Bouncing The impulse required to bring an object to a stop and then throw it back again is greater than the impulse required merely to bring the object to a stop.

Happy Sad Physics Spheres

Concept Checking Questions A lunar vehicle is tested on Earth at a speed of 10 [km/h]. When it travels as fast on the moon, is its momentum more, less, or the same? When you ride a bicycle at full speed and the bike stops suddenly, why do you have to push hard on the handlebars to keep from flying forward.

Concept Checking Questions What does an airbag do to help you reduce damage to your head in a car accident? When jumping from a significant height, why is it advantageous to land with your knees slightly bent?