# Velocity of a steel ball bearing due to magnetic force

1. Jan 22, 2013

### jonc1258

1. The problem statement, all variables and given/known data
Find the final velocity of a 5g steel ball bearing being pulled by a neodymium magnet with a pull force of 6.1 pounds (27.1 Newtons) in a straight line on a frictionless surface after being pulled for .1 meters

2. Relevant equations
F=MA

3. The attempt at a solution

f=ma
27.1 = .05a
a = 542m/s^2
The bearing travels for .1 meters, which is 1.85E-4 as far as it will travel in the first second (if the above solution for acceleration is correct), so t must be 1.85E-4 seconds.
v = (.1 m)/(1.85E-4 s) = 542m/s

As you can probably see by how unrealistic the numbers I came up with are, I'm not sure what to do. Could you maybe think about this in terms of kinetic energy? I gotta feeling that this problem is more complicated than I initially thought.

2. Jan 22, 2013

### haruspex

How many g in a kg?
No, it doesn't work like that. What equation do you know relating distance, speed and uniform acceleration?

3. Jan 22, 2013

### jonc1258

27.1 = .005a
a = 5420m/s^2

v$^{2}_{f}$ = v$^{2}_{i}$ + 2ad
v$^{2}_{f}$ = (0) + 2(5420)(.1)
vf^2 = $\sqrt{1084}$
v=32.9m/s

Yes?

4. Jan 22, 2013

### jonc1258

What if the first bearing were the trigger for a Gauss rifle?