Momentum and Impulse Notes

Momentum

To stop an object with momentum, a force must be applied against its motion for a period of time.

Momentum Factors

• Mass: Greater mass implies greater momentum.

• Velocity: Faster object motion implies greater momentum.

Example: A truck moving at 20 m/s has more momentum than a motorcycle moving at the same speed because the truck has larger mass.

Impulse

Impulse is the change in momentum of an object when a force is applied over a period of time. It is the product of force and time. Impulse equals change in momentum.

Impulse = net \ force \times time = change \ in \ momentum
J = F t = m \Delta v = \Delta p

Impulse can be changed with a large force and short time, or a small force over a longer time. More time lessens force.

Impulse and Momentum are vectors.

Newton's 2nd Law

F = ma

Acceleration can be written as the change in velocity per unit of time:

F = m \frac{v}{t}

Newton's 2nd Law in impulse form:

Ft = m\Delta v

Impulse and Time

Changing momentum can be achieved with a large force over a short time or a smaller force over a longer time.

Impulse Formula

Impulse (J) = Ft

More Time Means Less Force