Bellringer 9/30

• A skier leaves the horizontal end of a ramp with a velocity of 25.0m/s East and lands 70.0 m from the base of the ramp. How high is the end of the ramp from the ground?

Chapter 6: Momentum and Collisions

• Momentum – the product of the mass and velocity of an object

• Vector quantity – direction matches the velocity

Linear Momentum (p):p=mv

Momentum = mass x velocitySI units: kg●m/s

Momentum

Momentum

• If both of these objects are moving down the street at the same speed… which has the greater momentum?

• What about if the Mack truck is at rest… what object has the greatest momentum?

Roll Tide!!

Practice Problems

• A 2250 kg pick up truck has a velocity of 25 m/s to the east. What is the momentum of the truck?

p = 5.6x104 kg●m/s to the east

Practice

• A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the northwest. What is the total momentum of the child and

the bike together? What is the momentum of the child? What is the momentum of the bike?

Impulse-Momentum Theorem

• Impulse = product of the force and the time over which the force acts on an object

Impulse-Momentum TheorenFΔt= Δp or F Δt= Δp=mvf -mvi

Force x time interval = change in momentum

Practice

• A 1400 kg car moving westward with a velocity of 15m/s collides with a utility pole and is brought to rest in 0.30s. Find the force exerted on the car during the collision.

F = 7.0 x 104 N to the east

Stopping Distance

• Stopping times and distance depend on impulse momentum theorem

• Force is reduced when the time interval of impact is increased

Stopping Time

F t = F t

Practice

• A 2240 kg car traveling west slows down uniformly from 20.0m/s to 5.00m/s. How long does it take the car to decelerate if the force on the car is 8410 N to the east? How far does the car travel during the deceleration?

Impulse-Momentum Theorem