Carcass said:

Biped said:

If you drop a 1 tonne steel block off the top of the Eiffel tower, at the same time as a marble, they will both hit the deck at the same time.

As long as its in a vacuum

While the original hypothesis of the bullet horizontally and vertically is true, the Eiffel tower sketch raises the issue of practical effects.

I'd venture to suggest that the 1 tonne block would hit the sides of the tower and ricochet all the way down (owing to the shape of the tower) whereas the marble would probably hit once, and deflect outwards sufficiently to avoid further contact. Notwithstanding air effects, of course

For the mathematically minded, it goes like this

s=ut+(0.5 x at2 ) where t2 means "t squared"

In this equation, s is distance, u is initial velocity, a is acceleration and t is time. Since u is zero, this term goes away. Rearranging the equation for t, it becomes

t=SQRT (2s/a)

s will be the distance the bullets have to fall, say 1.5m (from the standing position). "a" is gravity, which is 9.81m/sec2. So the time of flight will be

SQRT(2 x 1.5 /9.81), or in round figures 550 ms.

This is schoolboy mechanics, air effects etc will have an influence, but not considerably so.