# Apparent forces problem, train of average speed and a difference in weight

1. Sep 16, 2012

### Trish1234

1. The problem statement, all variables and given/known data
While taking an eastbound train to work, a passenger of fixed mass finds that she weighs 542N. On the way home she weighs herself again while the train is at full speed and finds she weighs 543N. If she works 50km from home, how long is her commute if she lives at 40°S? (You may assume the average speed of the train is its full speed.)

2. Relevant equations
Dv/Dt=-fu
f=2Ωsinθ
Ω=7.292x10^-5 s^-1
F=-2Ω(sinθ)Mu

3. The attempt at a solution
First I tried solving the first equation for Dv/Dt getting -0.004687 km/s and didn't know where to go from here to find the time. Although I didn't feel right about it because I never used M. Then I found the last equation which includes M but I still don't know how to derive time from that equation. I know the solution is 10min, 18s but I don't know how to get that answer. Thank you for any help!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution