Change in momentum

Impulse In order to change the momentum of an object, an impulse must be applied to it.

Any moving object has momentum The magnitude of the impulse applied to the object, will equal the object’s change in momentum m v

What is the difference between impulse and change in momentum? The equation above does not mean that impulse and change in momentum are the same thing. It says that their amounts are the same.

Change in momentum by definition is:

The impulse applied to an object will equal the object’s change in momentum

When jumping, why will it be less painful if you flex your body when you land? The force applied to your body is inversely proportional to the stopping time. Therefore,

Conservation of momentum M=100 kg V=10 m/s

The total momentum before collision must equal the total momentum after collision Notice that to the right is positive and to the left is negative 100 to the right

In order to conserver momentum, after collision, the total momentum must be: to the right

Conservation of momentum Since the force on the bullet and gun must be equal in magnitude and are applied for the same length of time, the impulse must have the same magnitude for both.

Impulse = change in momentum Because the gun and bullet have the same impulse applied to them, they must have the same change in momentum

Conservation of momentum The change in momentum for the Terminator must be the same as the change in momentum of the shooter.

Why does landing on the air bag help to prevent death The air bag provides a longer stopping time and therefore a smaller force is applied to the jumper. Impulse = change in momentum Therefore:

How does a padded dash help to prevent injuries? The padded dash provides a longer stopping time and therefore a smaller force is applied to the jumper. Impulse = change in momentum Therefore:

Long barrel results in a larger time which will produce a larger change in momentum When you change the momentum of an object, you change its velocity Impulse = change in momentum

Why didn’t the professor move backward as fast as the marble moved forwad? The change in velocity is inversely proportional to the object’s mass. The professor’s mass was much larger than the marble’s, so he had a tiny change in velocity.

Is momentum conserved when a bullet is fired from a gun? Yes Their masses and velocities are different, but their change in momentum will be equal in magnitude and opposite in direction V gun V bullet M gun m bullet Magnitude of P gun = P bullet =

Why can a karate punch apply a large force? Because of the small stopping time Therefore:

As the stopping time approaches zero, the force approaches infinity Notice the inverse relationship between the time and the force