# Homework Help: Finding the force required to stop an object

1. Sep 11, 2011

### Nat3

1. The problem statement, all variables and given/known data
An object with mass $6.9*10^-3 kg$ and velocity 1300 m/s comes to a stop in 1cm. What force was applied to stop it?

2. Relevant equations
F = ma
$v^2=v_o ^2+2a\Delta x$

3. The attempt at a solution
$v^2=v_o ^2+2a\Delta x$
$0=(1300)^2+2a(0.001)$
$a=-\frac{(1300)^2}{2(0.001)}=-8.45*10^8 \frac{m}{s^2}$

$F=ma$
$F=(6.9*10^{-3} kg)(-8.45*10^8 \frac{m}{s^2})= -5.83*10^6 N$

Apparently that is not the correct answer. What did I do wrong?

Many thanks!

Last edited: Sep 11, 2011
2. Sep 11, 2011

### kuruman

1 cm = 0.01 m not 0.001 m.

3. Sep 11, 2011

### Nat3

Well now, I feel kind of silly :) At least it was a good mistake to make, being so simple to fix!

Thanks!