under what conditions can a person on a see-saw not jump up?
When two men with the same weight stand on either end of a see-saw, the see-saw is evenly balanced. If either man jumps up, he will, through the force of his leap, propel his side of the see-saw downward. Hence the man who jumps does not gain height, but rather propels his partner upward. The weight of the partner assures that the end of the see-saw remains under the feet of the man who jumps.
- why does something move?
- how can flowing water consume its momentum when it encounters an obstruction?
- why are the waves of descending rivers slower than the water flow of the river itself?
- why does a body move when something strikes it?
- why does waves look like crescents when viewed from the side?
- what happens to the waves when water crashed into an obstacle?
- what effects do the slope of the obstruction and the angle of impact have?
- why doesn't viscous water flow continually throungh a bent pipe?
- does the weight of water vary according to how one changes the slope of a pipe filled with water?
- how can one see that movement separates from its cause?
- where does the wave break?
- what causes cyclones?
- can a special dam influence the impact of the water?
- what must an especially strong dam look like?
- how can one simulate the collapse of a wave?
- how does air, once it is immersed, escape the water?
- what machine can be used to ram piles into the ground?