# Motion in Two or Three Dimension : Projectile motion

1. Feb 26, 2014

### physicos

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

A projectile is launched at a 60° angle above the horizontal on level ground. The change in its velocity between launch and just before landing is found to be Δv = vlanding _ vlaunch = -20 y^ m/s .
What is the initial velocity of the Projectile ?
What is its final velocity just before landing ?
2. Relevant equations

Δv = vlanding _ vlaunch = -20 y^
m/s .
3.The attempt at a solution
I considered :
Vox - Vfx = 0 and Voy - Vfy = -20
knowing that V²fy - V²oy= -2g (Yf-Yo) But I couldn't go further
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited: Feb 26, 2014
2. Feb 26, 2014

### haruspex

"+"?
What is the value of Yf-Yo?

3. Feb 26, 2014

### physicos

Yes , just saw it ! I edited the post !
I have no idea about Yf-Yo ,I couldn't guess it from the problem statement !

4. Feb 26, 2014

### haruspex

It is launched from, and lands on, the same level ground.

5. Feb 27, 2014

### physicos

so V landing = 0 ?? Because we know that v = sqrt(Vo²-2g(Y-Yo))

6. Feb 27, 2014

### PhanthomJay

No, you should check your algebra on that equation. But regardless, there are serious flaws in the problem statement. Did you word it correctly?