1. MOMENTUM Chapter 7

2. Definitions - 1 ■Momentum means inertia in movement or in other words So an object can have large momentum because it has large mass or large velocity or both. Note that momentum is a vector. ■If the momentum of an object changes, either the mass or velocity changes. Usually it’s the velocity that changes and a change in velocity is an acceleration. We know from Newton’s Second Law that a force is what causes acceleration and therefore a force causes a change in momentum. ■We can also conclude that the longer a force is applied, the greater the change in momentum.

3. Definitions - 2

4. Applications ■Science of Speed: MomentumScience of Speed: Momentum

5. Conservation of Momentum ■We saw that to change the momentum of an object we can exert an impulse on it. ■The force or impulse must be exerted by an object outside the object. ■So if no net force or net impulse acts on a system, the momentum of the system will not change. ■Law of conservation of momentum: –In the absence of an external force, the momentum of a system remains unchanged.

6. Demonstrations ■International Space StationInternational Space Station ■Momentum in FootballMomentum in Football ■Circus PhysicsCircus Physics ■Science of NFL FootballScience of NFL Football

7. Collisions

8. Example ■During a goal-line stand, a 75-kg fullback moving eastward with a speed of 8 m/s collides head-on with a 100-kg lineman moving westward with a speed of 4 m/s. The two players collide and stick together, moving at the same velocity after the collision. Determine the post-collision velocity of the two players. Momentum Before CollisionMomentum After Collision Fullback Lineman Total

9. Lab Simulations ■The Cart and the BrickThe Cart and the Brick ■Collision CartsCollision Carts –Elastic Collisions –Inelastic Collisions ■Time permitting, try other simulations on this pagethis page