Unit 5: Momentum and Impulse A soccer player strikes a moving ball during a game. What happens? We can use our known equations to: ◦ Predict motion before the strike. ◦ Predict motion after the strike. ◦ Calculate how the motion changes when the ball is struck. Now we will learn how force and duration of collision affect motion.

Unit 5: Momentum and Impulse Linear momentum of an object of mass m moving with velocity v is defined as the product of the mass and velocity.

Unit 5: Momentum and Impulse Momentum is so fundamental that Newton simply called it “quantity of motion.” Momentum is labeled p because of German physicist Gottfried Leibniz. He used the term progress to mean “the quantity of motion with which a body proceeds in a certain direction.”

Unit 5: Momentum and Impulse Momentum is a vector quantity. Its direction is the same as the object’s velocity. The SI units of momentum are the kg · m/s.

Unit 5: Momentum and Impulse Everyday examples of momentum: ◦ Coasting down a hill of uniform slope on your bike without pedaling or using the brakes. ◦ Rolling a bowling ball down a lane and rolling a playground ball down a lane  The more mass means more momentum (bowling ball vs. playground ball)  More velocity means more momentum (think of the damage hail can do!)

Unit 5: Momentum and Impulse Example: A 2250 kg pickup truck has a velocity of 25.0 m/s to the east. What is the momentum of the truck? (5.6x10 4 kg· m/s to the east)

Unit 5: Momentum and Impulse Here’s a fun Bill Nye video.Bill Nye video

Unit 5: Momentum and Impulse A change in momentum takes force and time. Impulse - Momentum Theorem or

Unit 5: Momentum and Impulse F Δt is called the impulse of the force F for the time interval Δt.

Unit 5: Momentum and Impulse Example: A 1400 kg car moving westward with a velocity of 15 m/s collides with a utility pole and is brought to rest in 0.30 s. Find the force exerted on the car during the collision. (7.0x10 4 N to the east)

Unit 5: Momentum and Impulse Stopping times and distances depend upon the impulse – momentum theorem. Highway safety engineers use the theorem to determine stopping distances and safe following distances for cars and trucks.

Unit 5: Momentum and Impulse Example: A 2240 kg car traveling to the west slows down uniformly from 20.0 m/s to 5.00 m/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? ( Δt = 4.00 s) (Δx = 50.0 m to the west)

Unit 5: Momentum and Impulse Force is reduced when the time interval of an impact is increased.

Unit 5: Momentum and Impulse Homework: ◦ Read articles on teacher page ◦ Complete the Worksheet -- Momentum and Impulse