physics
posted by susan .
A projectile of mass 0.840 kg is shot straight up with an initial speed of 22.9 m/s. (a) How high would it go if there were no air resistance? (b) If the projectile rises to a maximum height of only 8.71 m, determine the magnitude of the average force due to air resistance.

a. KE lost=GPE gained
1/2 m v^2=mgh solve for h
b. forceresistance=mass*accelrationfriction
so
1/2 m Vi^2=mghfrictionwork
1/2 m Vi^2=mghforce*h
solve for force knowing Vi, and the new h.