You are Here: Home >< Maths

# m2 collisions Watch

1. Can someone help me with part b?

A particle P of mass 3m is moving with speed 2u in a straight line on a smooth horizontal
plane. The particle P collides directly with a particle Q of mass 4m moving on the plane with
speed u in the opposite direction to P. The coefficient of restitution between P and Q is e.
(a) Find the speed of Q immediately after the collision.

Given that the direction of motion of P is reversed by the collision,
(b) find the range of possible values of e.

Would i make the final speed of P >0 or P<0 and please give me a reason why it is the one you have chosen?
2. For P to reverse, it's velocity must change sign, assuming you took P to be travelling right and right to be positive,
Put your speed of Q back into the equation for conservation of momentum in order to find some equation in e and u for the velocity of P, make this velocity <0 and solve for e.
3. (Original post by JN17)
For P to reverse, it's velocity must change sign, assuming you took P to be travelling right and right to be positive,
Put your speed of Q back into the equation for conservation of momentum in order to find some equation in e and u for the velocity of P, make this velocity <0 and solve for e.
That really helped me thank you.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 2, 2016
Today on TSR

### Anxious about my Oxford offer

What should I do?

### US couple arrested - 13 children chained up

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE