Initial Velocity of a projectile, how??? If I have a problem that says the x and y distance of a target from a starting position, and only gives the angle at which the particle is launched, how do I find the required initial Velocity for its launch? I've been given the following equations to work with: Vf = Vi + at xf = xi + Vit + (.5)at2 Vf2 = Vi2 + 2ad I've spent hours trying to find a solution like this and can't seem to get anywhere. At one point I wrote out a huge equation with a bunch of trig stuff and it said a human threw a ball at over 513m/s so I know it must have been wrong. One line I have written in my work says: 1.05=( Visin43 )/( Vicos43 ) - ( 4.9 * 9 )/( Vi cos 43 ) but I'm just asking in general, how do you do this???