A 1.0 kg projectile is fired from a point on the earths surface at an angle θ = 45° with the horizontal and with an initial velocity v = 30 m/s. Neglect any effects due to air resistance and find:
a) What is the kinetic energy of the projectile when it reaches the highest point on its trajectory?
b) How much work was done in firing the projectile?
total mechanical energy = KE + PE
KE_i + PE_i + W = KE_f + PE_f
The Attempt at a Solution
I'm not sure how to start this problem, or how to tackle it. I'm assuming I have to use the second equation? I let KE = 1/2 mv^2, m=1.0kg, v=30m/s. Then PE=mgh, m=1.0kg, g=9.81m/s/s, h=?. Then W=Fdcosθ, F=?, d=? cosθ=cos45°. Then I'm sort of stuck... There's a lot of values missing and I'm not sure how to solve or where to start.
Any help would be appreciated, thank you.