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.

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.

Sure, I'd be happy to help you with this question.

In the context of the brakes on a train being applied and the train decelerating, let's analyze each term in the first law of thermodynamics equation ΔU = ΔQ + ΔW:

1. ΔU (change in internal energy):
The change in internal energy (ΔU) refers to the difference in energy stored within the system. In this case, as the brakes are applied and the train decelerates, the internal energy of the system decreases. Therefore, ΔU is negative.

2. ΔQ (heat supplied to the system):
In the context of the train's brakes, ΔQ refers to the heat transfer associated with the braking process. When brakes are applied, they generate friction with the train's wheels, which causes heat to be generated. This heat is supplied to the system and typically represented by ΔQ. In this case, ΔQ is positive, as heat is being supplied to the system.

3. ΔW (work done on or by the system):
In the context of the train's brakes, ΔW represents the work done on or by the system. When the brakes are applied, the friction between the braking mechanism and the wheels requires a transfer of energy. In this case, as the brakes work to slow down the train, the work is being done on the system (train). Therefore, ΔW is negative.

To summarize:
- ΔU (change in internal energy) is negative.
- ΔQ (heat supplied to the system) is positive.
- ΔW (work done on the system) is negative.

Remember, the signs depend on how the variables are defined and the conventions used in the specific problem. It's always a good idea to clarify any assumptions or conventions with your instructor or within the context of the problem.