An object in motion remains in motion and an object at rest remains at rest unless acted upon by an outside force.

 

Inertia—the tendency of an object at rest to remain at rest

·      All objects have inertia—the greater their mass, the more inertia they have

·      For example, it is harder to move a bowling ball than a tennis ball because the bowling ball has more mass and therefore more inertia

 

Momentum—the tendency of a moving object to remain moving

·      Momentum=mass * velocity

·      p = mv

·      The more momentum an object has, the more force is needed to stop its motion

·      When objects collide, momentum is always conserved—that is, momentum is the same before and after the crash

·      Ex. What has more momentum, a 60kg runner moving at 5m/s or an 80 kg runner moving at 4 m/s?