Motion in Two or Three Dimension : Projectile motion

[physicos]

Homework Statement

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^→ = v^→_landing _ v^→_launch = -20 y^{^} m/s .
What is the initial velocity of the Projectile ?
What is its final velocity just before landing ?

Homework Equations

Δv^→ = v^→_landing _ v^→_launch = -20 y^{^}
m/s .
3.The attempt at a solution
I considered :
V_ox - V_fx = 0 and V_oy - V_fy = -20
knowing that V²_fy - V²_oy= -2g (Y_f-Y_o) But I couldn't go further

Homework Statement

Homework Equations

The Attempt at a Solution

 

[haruspex]

V_ox + V_fx = 0 and V_oy + V_fy = -20

"+"?

knowing that V²_fy - V²_oy= -2g (Y_f-Y_o)

What is the value of Y_f-Y_o?

 

[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 !

 

[haruspex]

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

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

 

[physicos]

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

 

[PhanthomJay]

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

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