Lost on Projectile motion problem

[exk4]

Homework Statement

A marble is thrown horizontally with a speed of 12.0 m/s from the top of a building. When it strikes the ground, the marble has a velocity that makes an angle of 30.3 ° with the horizontal. From what height above the ground was the marble thrown?


-im lost at where to begin

Homework Equations

The Attempt at a Solution

 

[JaredJames]

I think the key in this question is whether or not you are ignoring air resistance?

Jared

 

[exk4]

yes, while ignoring the air resistance

 

[JaredJames]

If there is no air resistance, there is nothing acting to decelerate the ball in the horizontal plane. The balls horizontal velocity is a constant 12m/s.