Conservation of Momentum

In an elastic collision, ——— energy is conserved

Kinetic

Kinetic energy

the energy an object or particle has due to its motion

A basketball player passes a ball to a teammate

-0.05 ms

A 50 kg boy runs and jumps with a forward velocity of 1.5 m/s into a 125 kg stationary boat. What is the final velocity of the boy/boat system? 0.43 m/s, forward 0.43 m/s, backward 1.1 m/s, forward 1.1 m/s, backward

0.43 m/s, forward

A ball has a mass of 0.25 kg and is moving to the right at 1.0 m/s. It hits a ball of mass 0.15 kg that is initially at rest. After the collision, the 0.15 kg ball moves off to the right with a velocity of 0.75 m/s. What is the final velocity of the 0.25 kg ball?

0.55 m to the right

A ball has a mass of 0.25 kg and is moving to the right at 1.0 m/s. It hits a ball of mass 0.15 kg that is initially at rest. After the collision, the 0.15 kg ball moves off to the right with a velocity of 0.75 m/s. What is the final velocity of the 0.25 kg ball?

0.55 m/s to the right

In a game of pool a 0.4 cue ball is traveling

0.56

In a game of pool, a 0.4 kg cue ball is traveling at +0.80

0.56

A train can has a mass of 10000 kh and is moving at +3.0m/s. It strikes an identical train car that is at rest. The train cars combine. What is the magnitude of the final velocity of the combined cars?

1.5 m/s

A bowling ball has an initial momentum of +30 kg m/s and hits a stationary bowling pin

17kg x m/s

An empty 2500 kg train car is headed northbound at a velocity of 5 m/s. I had of the first car an empty 1500 kg car is headed northbound on the same track at 1 m/s. The faster train bumped into the slower when it combined into one train. What is the velocity of the two car train?

3.5 m/s

Momentum data about the same objects in the same closed system is shown below. What value should be in place of the X? 3.4 3.5 3.6 3.7

3.6

A 35-gram stainless steel ball on a track is moving at a velocity of 9 m/s. On the same track, a 75-gram stainless steel ball is moving at a velocity of -7 m/s. After colliding, the 35-gram ball moves at a velocity of -15 m/s. Assume there is no net force on the system. What is the velocity of the 75-gram ball after the collision? Round to the nearest tenth. -4.2 m/s -0.5 m/s 0.5 m/s 4.2 m/s

4.2 m/s

inelastic collision

A collision in which the final kinetic energy is less than the initial kinetic energy. A perfectly inelastic collision occurs when the objects move as one object after they collide so momentum is conserved, energy is conserved and the maximum amount of kinetic energy is converted. Not all inelastic collisions are perfectly inelastic collisions. Most inelastic collisions are simply inelastic collisions, convert kinetic energy to potential energy noise or heat, and create potential energy by deforming an object

closed system

A group of related objects that interact and form a complex whole without being affected by the outside forces

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. When the carts collide, they hook together. Assume that positive momentum is to the right. Which graph best represents the momentum of both carts over time, before and after the collision?

B

Two identical carts travel at the same speed toward each other and then a collision occurs. The graphs show the momentum of each cart

B

Elastic example

Ball bouncing and bumper cars colliding

Train car a is at rest when it is hit by train car b. The two cars which have the same mass stick together and move off after the collision. How does the final velocity of train cars A and B after the collision compared to the initial velocity of train car B before the collision

Define velocity is half of train car, Bs initial velocity

Momentum is 40120kgxm/s with mass of 1180

Divide momentum by mass to get velocity

Inelastic collision

Door being slammed and hat being sat on

Conditions for an inelastic collision in a closed system

Energy and momentum are conserved. One object may be stationary before an inelastic collision.

Identify the conditions for an elastic collision in Las closed system

Energy is conserved, velocities may change, momentum is conserved, kinetic energy is conserved, and one object may be stationary before the elastic collision.

A collision in which some kinetic energy is lost

Inelastic collision

A girl is standing still in the middle of a baseball field.

Inelastic since the girl moves in the same direction as the thrown ball

Two grocery carts have the same initial total momentum. The two carts collide, and now cart B has a greater final velocity. Which best describes the final total momentum of both the carts compared to the initial total momentum? It is less if cart B has a smaller mass. It is greater if cart B has a greater mass. It is the same if no external forces are added. It depends on the masses of cart A and cart B.

It is the same if no external forces are added.

A collision in which the objects become one and move together

Perfectly inelastic collision

Which equation best describes the law of conservation of momentum

Pi = Pf

In a lab two identical lab carts (m=1.0 kg) travel toward

The experiment did not occur in a closed system

A rubber bullet of mass m is fired from a rifle into a stationary block of 25 m. The bullet remains in the block and both the bullet and the block move off with a common velocity. Assume this is an inelastic collision in a closed system. Which best describes the final momentum of the bullet/block? The final momentum of the bullet/block is zero. The final momentum of the bullet/block is equal to the initial momentum of the bullet. The final momentum of the bullet/block is less than the initial momentum of the bullet. The final momentum of the bullet/block is more than the initial momentum of the bullet.

The final momentum of the bullet/block is equal to the initial momentum of the bullet.

Two or more objects collide and stick together to become one object with one velocity.

The individual masses combine. All objects have the same velocity

Law of conservation of momentum

The law that states the total momentum of all interacting objects must remain the same Pi=pf

For a movie stunt, an empty truck with a mass of 2000 kg goes 10 m/s and runs into a stopped car of mass 1000 kg. The truck then keeps moving and pushes the car along with it. If there are no other forces acting on this system, which best describes the results of the collision? The collision is perfectly elastic. Kinetic energy stays the same. The momentum after the collision is greater than the momentum before the collision. The speed of the combined vehicles is less than the initial speed of the truck.

The speed of the combined vehicles is less than the initial speed of the truck.

Total momentum (Ptot)

The sum of the momentum's in a closed system Ptot= p1+p2+...pn Ptot=m1 v1+ m2 v2+... mn vn P=mv

Two blocks are initially at rest with a compressed spring

The total momentum is zero

Object A and Object B are in motion when they collide with each other. They then continue in a new direction unaffected by any other forces. This is a closed system and the momentum is conserved.

This means that the sun of the momentum's of A and B before the crash is equal to the sun if the momentum's of A and B after the crash

Momentum (p)=mv

Unit of kg • m/s

elastic collision

a collision in which kinetic energy and momentum is conserved Two or more objects collide and bounce apart with separate velocities. They keep original masses but velocities change