# Homework Help: A ball is thrown

1. Sep 23, 2007

### Ecterine

A ball is thrown horizontally from the top of a building and lands a distance d from the foot of the building after having been in the air for a time T and encountering no significant air resistance.

If the building were twice as tall, the ball would have

a) landed a distance 2d from the foot of the building
b) been in the air a time 2T
c) been in the air a time T squareroot2
d) reached the ground with twice the speed it did from the shorter building

x=x0 + v0xt + 1/2at^2
vx = v0xt +axt
and vx^2 = V0x^2 +2a (xf - xi)

Are, I think, the right equations. I don't know what to do though :(

2. Sep 24, 2007

### Ecterine

D'oh, it was C. Thanks anyways :)

3. Sep 24, 2007

### CompuChip

Note that the other three are equivalent: if the ball is in the air for a time 2T and the horizontal velocity does not change (no resistance) it will land at a distance 2d and since the velocity is v = a T it would also go twice as fast. So if any of these were true, then the other three would be true as well. Only b and c are clearly contradictory, so you just had to decide which one of them was true