1. The problem statement, all variables and given/known data A 160-lb man carries a 25-lb can of paint up a helical staircase that encircles a silo witha radius of 20 ft. If the silo is 90 ft high and the man makes exactly three complete revolutions, how much work is done by the man against gravity in climbing to the top? 2. Relevant equations W= line integral of dot product of F(r(t)) -dot- r'(t) 3. The attempt at a solution My r(t)= (20cost, 20sint, 90) r'(t)=(-20sint, 20cost, 0) t is between 0 and 6pi I know that gravity is -9.8 in the k direction. However I don't know what to use for my vector field....or if I should be using a different r(t). At first I tried using <0,0,-9.8> -dot- <-20sint,20cost,0> but obviously that just gives me zero.