# Homework Help: Vector diagram - please check

1. Apr 17, 2012

### jsmith613

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
Please could someone check my vector diagram

could someone also help me with part (c)

2. Apr 17, 2012

### azizlwl

Part c.
Use conservation of energy.

3. Apr 17, 2012

### jsmith613

well:

0.5*m*u2 = 0.5*m*v12 + 0.5*m*v22

but how does this prove anything in relation to the diagram?

4. Apr 17, 2012

### Steely Dan

What is the condition for two vectors to be perpendicular to each other?

5. Apr 17, 2012

### space_buster

Please specify perfectly elastic or partially elastic ???

6. Apr 17, 2012

### jsmith613

there vector sum = initial magnitude

7. Apr 17, 2012

### jsmith613

does not specify - just states "elastically"

8. Apr 17, 2012

### Steely Dan

Well, that's the condition for conservation of momentum. It's not a direct proof that the paths are perpendicular to each other. A direct proof of that is to take the inner product (or dot product, depending on what you call it) of the two final momentum vectors, and ensure that the result is zero (that is the definition of perpendicular vectors).

9. Apr 17, 2012

### jsmith613

well i have given you all the information I have
apparently it has something to do with Pythagrous but no idea what?