the first law of thermodynamics can be expressed with the equation ΔU=ΔQ+ΔW

where ΔU is the change of internal energy,ΔQ is the heat supplied to the system. Apply the first law to the brakes of a train as the brakes are applied and the train decelerated. you need to account for each term in the equation with reference to this context and explain whether each term is positive , negative of zero.

PLEASE I REALLY NEED SOMEBODY TO HELP ME OUT ASAP WITH THIS QUESTION.

1 answer

the braking force is opposite to the direction of motion, so we are doing negative work on the train
delta W is negative

Are we putting heat into the train? I think not. In fact heat is going out into the air as the brakes heat up.
delta Q is negative

So I suspect that the internal energy of our train system is dropping fast.