Question

prove that you are genius...answer is -1500J

Answer 1

2(a)20 = 100 a is effective accln
a= 2.5
therefore drag = 7.5
work done= 10*7.5*20 = 1500
EDIT:
(2as= v^2 -u^2)
now because of drag or air resistance the object is not falling with g but acceleration less than g.
(g - accln due to air resistance)
i find the net downward acceleration is 2.5m/s2
so the upward acceleration due to drag is 7.5m/s2. now calculate work = force(ma)*displacement.