Originally Posted by **HeliosV** My brother *is* my brother, but it does make sense in some kind of way.
Ok new example: if 2 weights weigh 50 pounds each, and they are placed on opposite sides of a lever and fulcrum, why does one weight lift up when the forces exerted are the same? |

This is a see-saw.

If the equal weights are placed at equal distances away from the pivot point, then the torques each one applies are equal and opposite, so no rotational acceleration occurs.

If the distances from the pivot point are different, then because torque is

$\displaystyle \tau = r \times F$

and even though F is the same, r is not, so the torques applied by each weight differ. Therefore, there will be a net torque equal to the difference in the individual torques, the see-saw will undergo rotational acceleration and it will tip over.

You can do this experiment for yourself. Make a see-saw using a long, wooden, ruler and a big blob of blue-tac. Then, get two

*different* weights and figure out the two different distances that both can be placed so that the torques are the same. You'll find that the see-saw either doesn't tip over or it tips over slowly (because of inaccuracy). Another way to do it is to go to a see-saw in a park and find the bit of the see-saw you need to sit to balance it (unless you weight the same as your brother!)