Work problem. Right answer, wrong units

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 10K views · last reply
Science Advisor
Gold Member
Messages
1,753
Reaction score
143
My answer should obviously be in Newtons, but I'm getting Netwon meters.

An aquarium, 2 m long, 1 m wide, and 1 m deep is full of water. Find the work needed to pump half the water out of the aquarium. (The density of water is 1000 kg/m3.)
Handwritten derivation of work for pumping water: W = integral of f(x) dx, f = F = ma, m = rho times volume, leading to W = 9.8 times 2 times 1000 integrated over y from 0 to 1/2, and a final result of 2450 with units kg m^2/s^2 = N m.


In a similar example in the book, they do the problem the same way, but they just throw the units in at the end, after they've computed the answer. I could do the same on this homework problem and get full credit, but I just got to know... :smile:


 
Physics news on Phys.org
What makes you think that unit is wrong? What's the definition of work?
 
oops... It's getting late. I don't know why I was expecting Newtons. Thanks!