Define momentum Define impulse Relate impulse and momentum to everyday

In life - momentum describes something “on a roll” that is difficult to stop. In physics - momentum describes a quantity of motion. If an object is in motion then it has momentum. "mass in motion" Inertia Velocity

Momentum is a vector quantity Momentum is a vector quantity. It has the same direction as the objects velocity. p = mv Every moving object has momentum. To bring the object to rest we must apply a force to change this momentum to zero.

Bus football sprinter skateboarder slapshot statue race car Estimate the mass of each object and estimate its velocity to try to order the following objects in increasing momentum: statue Bus football sprinter skateboarder race car slapshot

PHYSICS A textbook at rest has no momentum. To make the book move you must overcome friction and the book’s inertia by applying a force. A force accelerates the book, giving it a velocity. The book now has forward momentum, and the inertia of the book continues the motion forward.

Impulse Momentum

To change an objects motion (momentum) we need to apply an unbalanced force. Increased momentum Unbalanced Force Decreased momentum Unbalanced Force

The amount of unbalanced force and the time during which the force is applied is the impulse. I = F·t Impulse equals force multipled by time F t

A force for a given amount of time will result in a mass undergoing a change in velocity. m·∆v I = F·t = Impulse equals a change in momentum F t 0 m/s 10 m/s

2 seconds 100 N 20 kg 0 m/s 10 m/s F·t m·∆v = = 100·2 200 20·10 200

F·t = m·∆v = -200 20·(-10) (-50)· -200 4 20 kg 50 N 10 m/s 0 m/s 4 seconds 50 N 20 kg 10 m/s 0 m/s F·t = m·∆v = -200 20·(-10) (-50)· -200 4

TWO ways to apply a large impulse to an object and make a BIG change in momentum – apply a LARGE force for a small time, Impulse = (Force) (time) apply a small force for LONG time. Impulse = (Force) (time)

Stopping a passenger requires an impulse. Inertia keeps the passenger moving forward with the same momentum as before (speed of the car). Impulse = (Force) (time) Stopping a passenger requires an impulse. If the time can be made longer then the stopping force will be made smaller. Small forces will cause fewer injuries to passenger.

In every sport where you hit something you are told to “follow through Following through increases the TIME that your force acts on the object, which makes for a larger change in velocity (momentum)

·t F m ∆v = m m 500 (.2) = + 200 m/s 0.5 500 (.1) = + 100 m/s 0.5 Follow through 0.5 500 (.1) = + 100 m/s No follow 0.5