Ok so here is the situation: There is a 20 pound ball hanging from a string in a loop. below the ball, there is another identical string attached loosely in a loop. So here is what happens. A person puts a rod through the bottom loop and yanks really hard and the result is the bottom string breaks. However if you put the rod through the same loop at the bottom and then push really slowly the top sting snaps and the ball falls. Why does this happen?