# Homework Help: Projectile Motion Explaination

1. Oct 29, 2005

### quicknote

Two spheres are launched horizontally from a 1.0m high table. Sphere A has a mass of 1.0kg and is launched with an initial speed of 5.0 m/s. Sphere B has a mass B has a mass of 0.4kg and is launched with an inital speed of 2.5 m/s.

Compare the times for each sphere to hit the floor.
Compare the distances that each travels from the edge of the table.

I just need some explaination in the concept of the first question.
I know the the equation used to find the time is $$t = \sqrt{ \frac {2h}{g}}$$ and the answer is 0.45s
But I don't understand why the different masses and velocities don't have an effect on the time to fall.

2. Oct 29, 2005

### mathmike

the same reason that if you fire a bullet horizontally and drop one at the same instant they will hit the ground at the same instant

3. Oct 29, 2005

### whozum

The initial velocity is perpendicular to the acceleration and has no effect on it, and the acceleration of gravity is independant of mass