# Momentum and Impulse Questions

• amyiish
Then use the given information to solve for the final velocity of the system, which will be the same for both the man and the log. In summary, the conversation discusses two problems involving momentum and impulse. The first problem involves a swimmer standing on a raft and running off with a velocity of +5.3 m/s. The question asks to find the recoil velocity of the raft assuming no friction or resistance due to water. The second problem involves a football receiver being tackled by a player running at a velocity of +5.0 m/s. The question asks to find the mass of the receiver assuming conservation of momentum.
amyiish
Can anyone help me solve these questions on momentum and impulse? Thank you!

1. A 55 kg swimmer is standing on a stationary 235 kg floating raft. The swimmer then runs off the raft horizontally with a velocity of +5.3 m/s relative to the shore. Find the recoil velocity that the raft would have if there were no friction and resistance due to the water.

2.In a football game, a receiver is standing still, having just caught a pass. Before he can move, a tackler, running at a velocity of +5.0 m/s, grabs him. The tackler holds onto the receiver, and the two move off together with a velocity of +2.6 m/s. The mass of the tackler is 119 kg. Assuming that momentum is conserved, find the mass of the receiver.

:yuck:

Hello amyiish, and welcome to PF.

In order to get help, you should show us some attempts and share some thoughts on the problem with us. After doing so, we'll be glad to lead you through if you get stuck.

Edit: also, such questions belong to the 'Homework & Coursework section', but don't repost, it will be moved to that section soon enough, I assume.

Last edited:
I figured out how to do the second one, but I still need help on the first one. I'm not sure what equation(s) I'm supposed to use. Pretty much clueless, actually..

amyiish said:
I figured out how to do the second one, but I still need help on the first one. I'm not sure what equation(s) I'm supposed to use. Pretty much clueless, actually..

It's a conservation of momentum problem, too. Still clueless?

Should I use: mv1 + mv2 = m(1+2)v(1+2) ?

Oh, I got it! I just forgot it would be negative. Thank you. :)

amyiish said:
Should I use: mv1 + mv2 = m(1+2)v(1+2) ?

Simply use conservation of momentum. The velocity of both the man and the log equals zero first, which sets one side of your equation equal to zero.

## 1. What is momentum?

Momentum is a physical quantity that is a measure of an object's motion. It is calculated by multiplying an object's mass by its velocity.

## 2. How is momentum different from inertia?

Inertia is an object's resistance to changes in its motion, while momentum is the measure of an object's motion itself. Inertia depends on an object's mass, while momentum depends on both mass and velocity.

## 3. What is the relationship between force and momentum?

According to Newton's Second Law of Motion, the force acting on an object is directly proportional to its change in momentum over time. This can be represented by the equation F = ma, where F is force, m is mass, and a is acceleration.

## 4. How does impulse affect an object's momentum?

Impulse is defined as the change in an object's momentum over time. When a force is applied to an object for a certain amount of time, it causes a change in the object's momentum. The greater the impulse, the greater the change in momentum.

## 5. Can an object have momentum without moving?

Yes, an object can have momentum without moving if it has mass and is at rest. This is because momentum depends on an object's mass, not just its velocity. However, an object must be in motion to have kinetic energy, which is the energy associated with its momentum.

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