- #1

knowlewj01

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## Homework Statement

An engine of mass 100 tonne pulls a train of mass 400 tonne along a horizontal track. There is a horizontal frictional force of size 1 kN acting on the engine and a horizontal frictional force of size 20 kN acting on the train. Find the tension in the couplings between the engine and the train at the instant when the speed of the train is 80 kmh-1 and the engine is exerting a power of 4000 kW.

(1 tonne = 1000 kg.)

## Homework Equations

P = Fv

[maybe conservation of energy?]

## The Attempt at a Solution

What I have done is, first turn all the units into SI, work out the force provided by the engine and then resolve horizontally to find the Tension. This did not really work for me because the force provided by the engine turned out to be about 180 kN. I'm not sure what I'm doing wrong, have I perhaps made the wrong assumption that the system is at a constant speed? Also given that the masses were involved in the brief i guess they have to be used somewhere. Anyone have any hints/tips? Thanks