# What is the magnitude of the force?

1. Feb 20, 2015

### nmi13

1. The problem statement, all variables and given/known data
Mike is training for a strongman competition. Using a rope, Mike is pulling a locomotive of mass 2.00 x 10^4 kg coupled to two 0.50 x10^4 kg rail cars. Mike causes the train to accelerate at 0.045 m/s^2 . What is the magnitude of the force in the coupling between the locomotive and first car?

Mass of locomotive = 2.00*10^4 kg
Mass of each rail cars = 0.5*10^4 kg
acceleration = 0.045m/s^2

2. Relevant equations
F= ma

3. The attempt at a solution
I just don't know exactly how to begin to answer this question. I am unable to find any similar questions to help me out with. A nudge in the right direction is all I need. Thank you!

2. Feb 20, 2015

### Quantum Defect

Draw a free body diagram for the rail cars. I.e for the last car, there is a net force pulling the car forward such that the acceleration of the last car is 0.045 m/s^2. What is that force? That force is equal and opposite the force at the back of the first car, pulling back. At the front of the first car, there is also a force pulling it forward. The net force on the first car is such that the first car is accelerating at 0.045 m/s^2. What is the force at the front of the first car?