# Homework Help: Relationship between initial speed of cart and distance repelled by magnets.

1. Nov 8, 2008

### ongfufu

1. Determining the relationship between initial speed of a cart (with magnets, aligned with and moving towards magnets on a wall) and the stopping distance from the wall)

2. Kinetic energy(Ke)=Magnetic potential energy(Mpe)
Ke=mv^2/2
Mpe=km1m2/r
mv^2/2=km1m2/r
v is proportional to (r^1/2)

K$$_{e}$$=$$\frac{mv^{2}}{2}$$
M$$_{pe}$$=k$$\frac{m_{1}m_{2}}{r}$$
$$\frac{mv^{2}}{2}$$=k$$\frac{m_{1}m_{2}}{r}$$
v is proportional to $$\frac{1}{\sqrt{r}}$$

3. I think speed is proportional to inverse square root of the stopping distance.

So a cart with magnets taped to the front end is pushed through a photogate, which measures speed of the cart, towards the wall with magnets aligned with those on the cart. The cart starts 20cm away from the wall. By varying the speed of the cart, I measured how far the cart was repelled by the magnets on the wall.

Last edited: Nov 8, 2008