Deriving Projectile Motion Equations from Initial Conditions

[charris316]

Homework Statement

Derive algebraic expressions for the range and total time-of-flight of a projectile launched with initial speed v, from a height h, and at an angle Q, above the horizontal. We were given the final equations but I am unsure of how to derive them.

Homework Equations

range=vt-.5gt^2, where g is the acceleration due to gravity and t is the time in seconds.

time= (vsinQ+((vsinQ)^2+2gh)^.5)/g

The Attempt at a Solution

Considering the ball, after it has been launched:
Fx=0
Vox=vcosQ
Fy=mg
Voy=vsinQ

?

 

[willem2]

That equation for range is wrong.

The first step is to find an the height as a function of time.
Set this to zero to find the time-of-flight.