# Homework Help: Projectile motion - have i done this correctly?

1. Sep 8, 2008

### Mglafas

I'm unsure whether I have done the following problem correctly :)

1. The problem statement, all variables and given/known data

A ball is kicked at from the slope as shown.
When will the ball hit the slope?

http://img90.imageshack.us/img90/8084/slopevi0.th.jpg [Broken]

2. Relevant equations

The distance travelled can be expressed in two components:
Sx=vt
Sy=0.5gt^2

The displacement compontents can also be expressed in terms of tan(a)
tan(a)=Sy/Sx

3. The attempt at a solution

Substituting we get:
Sy=Sx*tan(a)
0.5gt^2=vt*tan(a)
0.5gt=v*tan(a)
t=[2v*tan(a)]/g

Is this correct?

Last edited by a moderator: May 3, 2017
2. Sep 8, 2008

### mezarashi

Your approach is looks sound to me. The idea is you want to find the components x and y that match the slope of the ramp.

3. Sep 8, 2008

### LowlyPion

That looks fine.

What you apparently developed is the equation for angle of the ball, as a function of t, from some point down the slope, and by setting the angle of tan to θ, that's where it hits and you have the value for the time now as a function of Vo and θ. Good job.

Last edited: Sep 8, 2008