# Conservation of momentum + elastic collision

• Return
In summary, the conversation discusses a problem involving the conservation of momentum and an elastic collision between two blocks of different masses on an incline. The question asks for the speeds of the blocks after the collision and how far the smaller block will go up the incline. The use of conservation of energy and momentum is suggested to solve the problem.

#### Return

[SOLVED] Conservation of momentum + elastic collision

Hey guys, I couldn't even start this one, tried to think about it, but I'm hitting a blank

A block of mass m = 2.20 [kg] slides down a 30 degrees incline which is 3.60 [m] high. At the bottom, it strikes a block of mass M = 7.00 [kg] which is at rest on a horizontal surface. (Assume a smooth transition at the bottom of the incline.) If the collision is elastic, and friction can be ignored, determine A) the speeds of the two blocks after the collision and B) how far back up the incline the smaller mass will go.

know: m = 2.20kg
theta = 30 degrees
h = 3.60m
M = 7.00 kg

Ok so I don't understand how to find the velocity when the blocks start. I know that the collision in elastic so momentum is conserved, but should I use conservation of energy or dynamics to solve for it?

Any help would be great. Thank you!

Return said:
I know that the collision in elastic so momentum is conserved, but should I use conservation of energy or dynamics to solve for it?

Hi Return!

No … all collisions conserve momentum.

"elastic" means that energy is conserved also.

Does that help?

lol oh yea, that's a slap in the head ty for the reminder

I got this one over lunch, so looks like I'm good, used a combination of conservation of momentum and conservation of energy.

## 1. What is conservation of momentum?

Conservation of momentum is a fundamental law in physics that states that the total momentum of a closed system remains constant. This means that the total momentum before and after a collision or interaction between objects is the same.

## 2. What is an elastic collision?

An elastic collision is a type of collision in which kinetic energy is conserved. This means that the total kinetic energy of the objects before and after the collision is the same. In an ideal elastic collision, the objects involved bounce off each other without any loss of energy.

## 3. How is momentum conserved in an elastic collision?

In an elastic collision, momentum is conserved by the principle of action and reaction. This means that the total momentum of the two objects involved in the collision is the same before and after the collision. This can be mathematically represented by the equation: m1v1 + m2v2 = m1v1' + m2v2', where m is mass and v is velocity.

## 4. What are some examples of elastic collisions?

Some examples of elastic collisions include a game of billiards, a bouncing ball, and a pendulum swinging back and forth. In all of these scenarios, the objects involved are able to bounce off each other without any loss of energy, resulting in an elastic collision.

## 5. How does conservation of momentum relate to real-life situations?

Conservation of momentum is a fundamental law of physics that applies to all interactions between objects, making it relevant in countless real-life situations. For example, it explains why a person on a skateboard moves forward when they push off a wall, or why a rocket is able to launch into space by expelling exhaust gases.