# Magnetic force vs gravity

1. Aug 10, 2008

### spidey

i have two magnets and i want to repel one magnet against gravitational force upwards..so how powerful the magnet should be?i can calculate the gravitational force using newton's law f=gm1m2/r2 where m1 is mass of earth and m2 is mass of one magnet...so the magnetic force should be greater than this force ....help me...

2. Aug 10, 2008

### quark1005

You require the force on the magnet to be equal to the force of gravity, as you said.

$$F = I \Delta l B sin \theta = \frac{Gm_{1}m_{2}}{r^{2}}$$

3. Aug 10, 2008

### tiny-tim

Hi spidey!

Technically, it's Gm1m2/r2,

but we can write Gm1/r2 = g, the usual gravitational constant at the Earth's surface,

so f = Gm1m2/r2 = m2g.