# Find magnitude, help

## Homework Statement

A ball of mass 350g is travelling with a speed of 4m/s when it hits at right angles a fixed vertical wall. The ball rebounds with a speed of 3m/s. Find the magnitude of the impulse exerted by the ball on the wall. Using a simple diagram show the direction of velocities and the impulse.

## Homework Equations

m = 350g or m = 0.35kg v1 = - 4m/s^-1 v2 = 3m/s^-1

Magnitude = mv2 – mv1

## The Attempt at a Solution

Magnitude = 0.35 3 – 0.35(- 4)

Magnitude = 1.05 – 1.4

Magnitude = - 0.35

Hi can some one check this equation for me please.

Also is there a unit to simbolize magnitude? and is the final answer 0.35 given in joules???

Last one how would i draw a simple diagram showing the direction of velocities and the impulse???

thank you

However, being a magnitude , it should have positive sign.

As for the units, just work them out by what you have in the equation.
I'm sure you know the units of m and v (and you're given them, anyway), so just use those.

Start drawing a diagram showing the velocities only, I'm sure you'll understand in what direction should the impulse go.

i've calculated wrong.
it should have been.

Magnitude = 1.05-(-1.4)
= 2.45

kg m/s

is the final answer given in N??

N is kg m/s2, but you only have kg m/s.

So you can either leave it as kg m/s or rewrite it as..?

thank you for you help, but i can't get there, to be honest, i started studying after 15 years and this thing is doing my head, i have to handle my course work tomorroy, and i'm still half way.lollol

Just look at how the RHS of the two equations below is altered and you will know how to change the LHS as well.

N = kg m/s^2

? = kg m/s

i think the answer is Ns

It is indeed.