# Homework Help: Magnetic Forces acting upon a slider on rails

1. Jan 19, 2010

### Peto

A 0.40kg metal slider is sitting on smooth (frictionless) conducting rails as shown below. What is the magnitude and direction of the acceleration of the slider?

Given,

B = 3.0T I = 5.0A m = 0.40kg
R = either 0.1m or 0.05m, im not sure if you half it because its a raidius.

How can you figure out the acceleration of the slider?
or would the acceleration be zero since the rail with the current hading left would counteract the rail with the current heading right? therefore acceleration = 0 and magnitude would not be applicable?

I'm not sure what to do here
thanks in advance for any help!

2. Jan 20, 2010

### rl.bhat

What is the expression of the force on the current carrying conductor in a magnetic field?
0.1 m is the distance between the rails. It is also the length of the conductor sliding on the rails.

3. Jan 20, 2010

### Peto

The expression is F=BIl
so F=(3.0T)(5.0A)(1.0m)= 15N.
Then using F=ma the acceleration would be
a=F/m=(15N)/(0.40kg)=37.5m/s^2
so if that is the acceleration, then Which way would it accelerate? Towards the battery or away?

4. Jan 20, 2010

### Peto

Sorry the length is 0.1m so that would give a force of 1.5N and an acceleration iof 1.5/0.4=3.75m/s^2
in which direction ?

5. Jan 20, 2010

### rl.bhat

Use Flemming's left hand rule to find the direction of the force.