2x10^-7]-The work done is the same thing as saying the amount of energy transferred.Assuming no energy was lost to air resistance, then the amount of gravitational potential energy lost by the raindrop is the total work done, so we can sidestep the issue of forces entirely.Im not sure how you got the answer you did with the formula you describe. Remember that if the raindrop is falling at constant velocity,......
Then:
W = mass x acceleration_g x d
W = (7.2x10^-9)kg x 9.81m/s^2 x 4.5m
this works out to be:
[W=3.18x10^-7] or [W=3.2x10^-7]
The "work done" is the same thing as saying "the amount of energy transferred".
Assuming no energy was lost to air resistance, then the amount of gravitational potential energy lost by the raindrop is the total work done, so we can sidestep the issue of forces entirely.
I'm not sure how you got the answer you did with the formula you describe. Remember that if the raindrop is falling at constant velocity, the net force on it is zero (the work would be coming from whatever force got it moving in the first place). For this to be the case, there would be forces from gravity and air resistance, and the entire equation would be very difficult. Your formula is only really applicable for a constant force over a fixed distance, which is not applicable here. What we have here is a simple energy transfer, so it's easier to measure work that way.
