# Homework Help: Magnitude, net forces problem

1. Oct 12, 2007

### rcmango

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

A 41 kg hatch is thrown at a speed of 215 m/s and is immediately stopped once it hits something that lasts for a time of 5.6 ms.

So What is the magnitude of the average net force that acts on the hatch during the point that its hitting something?

2. Relevant equations

3. The attempt at a solution

where do i start?

2. Oct 12, 2007

### PhanthomJay

You should be familiar with the impulse/momentum equation. Or just use F_net=ma. Give it a try.

3. Oct 13, 2007

### rcmango

okay, so if i use the formula of F_net=ma

i don't know the net forces (newtons)

i don't know the mass or the acceleration (m*a)

i do know the velocity and the time.

so must i use an equation to find the acceleration? so i'm closer to my answer?

what do i need to solve for next?

4. Oct 13, 2007

### PhanthomJay

The mass is given. What's the equation to use to find acceleration when the velocity change and time are known?

5. Oct 13, 2007

### rcmango

the formula is a = chng velocity / chng time

so a = 215 / 5.6 ?

6. Oct 13, 2007

### PhanthomJay

watch units, the change in v is in m/s, and t is given in milliseconds(i.e., t =.0056 seconds).