Linear Momentum Physics Mrs. Coyle

Linear Momentum, p p= m v Momentum is a vector. The direction of momentum is the same as the direction of the velocity of the object. Unit: kg m/s or N s “Inertia in Motion”

Question 1: What has more momentum, a dump truck at rest or a pebble moving down a hill at 1m/s?

Question 2 How can you change the momentum of an object?

Impulse = Impulse =  p = m  v = Ft

Problem 1 Starting with Newton’s second law, show that for a constant force,  p = m  v = Ft.

To reduce the force of impact, increase the time of impact. For a given change in velocity,  p is constant :

Question 3: How do you have a better chance of winning in a water balloon toss contest?

Question 4: Why does a boxer “roll with the punches”?

Question 5: Why should you follow through in a serve when playing tennis, or when hitting a baseball?

Problem 2 A ball at rest has a mass 0.5kg and is kicked with a force of 40N. The impact lasts 0.2s. Find: a)The change in momentum of the ball. b)The final velocity of the ball. Answer: a) 8 Ns, b)16m/s

Problem 3 A football player of mass 130kg travelling at 12.0m/s collides with another player and comes to rest in 0.90s. What was the force of impact? Answer:1,733N

Impulse is the area under the curve in a graph of F vs t. F t

Some Engineering Applications

Question 6 Why are airbags used?

MARSEXPLORATIONMARSEXPLORATION

MARS LANDER AIR BAGS

Rover Exits the Lander

Applications in Engineering Household Items

MILK BOTTLES

THE EGG CARTON