# In projectile motion, why does an object that is vertically dropped down and an object that is horizontally launched reach the ground at the same time?

##### 1 Answer

Mar 7, 2018

Because acceleration due to gravity is

#### Explanation:

A dropped object accelerates downward at g. The time to the ground is given by

A projectile launched horizontally accelerates downward at g. The time to the ground is given by

where the vertical component of its velocity,

One condition: if the ground is not perfectly level from the site of the launch of the projectile to the impact area, that would change things.

I hope this helps,

Steve