Momentum n Momentum is inertia in motion momentum

Momentum n Momentum is inertia in motion momentum = mv

Momentum n n n Momentum is a vector What is the momentum of a 75 kg person who is jogging at a constant velocity of 2 m/s to the east? momentum = mv momentum = (75 kg)(2 m/s east) momentum = 150 kg·m/s east

Momentum and Collisions n TOTAL momentum is conserved mbeforevbefore = maftervafter

Example n n A 2000 kg car traveling 20 m/s east collides with another 2000 kg car at rest. The two vehicles move as a unit after the collision; what is the speed of the two cars? Ignore friction. Conservation of Momentum 10 m/s east

Example n A 60 kg person standing on ice catches a 5 kg ball that is traveling 10 m/s. How fast will the person be moving after the catch?

Example n A 60 kg person moving east at 2 m/s catches a 10 kg ball that is moving west at 20 m/s. What is the person’s new velocity if we ignore friction? 2 m/s 20 m/s

Example n A 0. 250 kg ball is moving east at 5 m/s on a frictionless surface. It collides with a 0. 800 kg ball at rest and they bounce apart (i. e. , it is an elastic collision). After the collision the 0. 250 kg ball is moving 2. 62 m/s to the west. n n n What is the total momentum before the collision? What is the total momentum after the collision? What is the velocity of the 0. 800 kg ball after the collision?

Change in Momentum n n n We can change the momentum of an object by changing its velocity. Newton’s Laws tell us that a force is required to change an object’s motion. Thus, to change an object’s momentum we need to apply a force.

Change in Momentum n n n A change in momentum is called Impulse = change in momentum Impulse = Δ(mv) Ft = Δ(mv)