Momentum

momentum... p=mv p=momentum m is mass in kilograms Momentum is inertia in motion p=mv p=momentum m is mass in kilograms v is velocity in m/s

Example 1: How can a truck with a mass of 10,000kg and a child with a mass of 22kg have the same momentum?

If the momentum of an object changes If the momentum of an object changes...either the mass has changed, velocity has changed or both. Since it is rare for mass to change, usually it will be a change in velocity which means we need to use our acceleration formula. What causes acceleration?

FORCE!! If a quick force is applied (bunt) rather than a force over a period of time (follow through) acceleration rates will vary. Also true is applying a stopping force over time, hence the value of air bags in a car.

Situation 1: To maximized the distance of a golf ball, the golfer will take a complete swing. Following through increases the time that the force is being applied.

Situation 2: If your brakes fail in your car and you have 2 choices to bring the car to rest: 1) hit the guard rail or 2) drive off the road into a corn field. Which do you pick and why?

Example 2: A truck with a mass of 5000kg and a velocity of 0.01m/s. If a small sports car with a mass of 700kg is in motion also, how fast must it travel to have an equal momentum to the truck?

Example 3: What is the momentum of a free falling rock when it strikes the ground? Mass of the rock is 4 kg and time in the air was 2 seconds?

In order to calculate the force of a strike (impulse) we must use the formula: F=change in momentum/change in time F=Δp / Δt F=(mvf –mvi) / Δt If the force is applied in an instant (bunt, chip) we negate the Δt.

Example 4: A 1400kg car moving west with a velocity of 15 m/s collides with a pole and is brought to rest in 0.03sec. What is the magnitude of the force exerted on the car during the crash?

Example 5: A 1kg basketball is bounced off the floor with a downward velocity of 29.4m/s and returns with a 19.6m/s velocity. What was the impulse force delivered to the floor?

Example 6: A 0.8lb baseball is pitched with a speed of 85mph and comes off of the bat at a speed of 105mph. What is the impulse force of the ball on the bat?

Impulse is greater when an object bounces because it requires more energy (force) to stop the object an throw it back than to just simply stop it.

Momentum is conserved when two objects are considered to be in a system. Rifle-Bullet system… Force is equal on both pieces of the system, but the bullet will travel further due to mass.

What happens if you and your best friend are both wearing rollerblades and stand close together. If you push off of each other, who will go further? Why?

Impulse

If there is a quick, almost instantaneous change in momentum (bounce) we say that an impulse force has been delivered. Fim= m(Δv) Fim is Force impulse in Newtons M is mass in kg Δv is a change in velocity

Example 1: A 1kg basketball is bounced off the floor with a downward velocity of 29.4m/s and returns with a 19.6m/s velocity. What was the impulse force delivered to the floor?

Example 2: A 0.8lb baseball is pitched with a speed of 85mph and comes off of the bat at a speed of 105mph. What is the impulse force of the ball on the bat?

Impulse is greater when an object bounces because it requires more energy (force) to stop the object an throw it back than to just simply stop it. How much force is need to stop the baseball in example 2?

Momentum is conserved when two objects are considered to be in a system. Rifle-Bullet system… Force is equal on both pieces of the system, but the bullet will travel further due to mass.

What happens if you and your best friend are both wearing rollerblades and stand close together. If you push off of each other, who will go further? Why?