1. Chapter 6 Momentum and Impulse

2. Momentum The product of an object’s mass and velocity: p = mv
Momentum, p, and velocity, v, are vector quantities, meaning they have magnitude and direction.
The units for momentum are
kg * m /s.

3. Momentum Examples…
A 61-kg man is traveling north in a 3200-kg car at 15 m/s. What is the momentum of the man? What is the momentum of the car? What is the total momentum of the man and car together?
How fast must an 11,000-kg truck travel to have the same momentum as the man and the car in the previous problem?

4. Impulse FΔt = Δp or FΔt = mvf - mvi
Since a net external force changes the
velocity of an object, it also changes the
object’s momentum.
If a net external force, F, is applied to an
object for a certain time interval, Δt, then
FΔt is the impulse of the force.
Impulse equals the object’s change in momentum.
FΔt = Δp or FΔt = mvf - mvi

5. Force and Momentum Examples
A 145-gram baseball is thrown to the right at 17 m/s. The first baseman catches the ball and brings it to rest in s. What force does the first baseman exert on the ball?
A 7.1-kg piece of wood is dropped from a cliff 83 meters above the ocean. What is the velocity of the wood when it hits the water?
If the water exerts an upward force of 140 N on the piece of wood, how long will it take for the piece of wood to come to a stop?

6. Stopping Distance Examples
A 3200-kg car is traveling east at 14 m/s when the driver steps on the brake pedal. The brakes apply a force of 9400 N to the west. How far does the car travel before it comes to a stop?
In the previous problem, what is the car’s velocity 1.0 second after the brakes are applied? How far has it traveled after 1.0 second?
560 kg of cargo is loaded into the back of the car in the previous problem. If the same brake force is applied, how long will it take the car to come to a stop and how far will it go?