- #1
Toe Jailor
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My physics book does this First Law of Thermodynamics example problem during the chapter that shows the steps into getting the solution. They say a drill bores a hole in a block (so doing work) and increases the temperature of the block. It then states the equation they're using: ΔU = Q - Wdone by block. They want to know how much work is done by the drill. So therefore, they alter the equation to ΔU = Q + Wdone by drill. So far this makes perfect sense.
Because no heat is exchanged (because there's no temperature differences between the drill and block), the equation becomes ΔU = 0 + Wdone by drill. But then they confuse me by saying ΔU = Wdone by drill = mCΔT. I am totally confused on why they equate ΔU and W to mCΔT, as mCΔT = Q. Q = 0, so mCΔT would also equal zero I'd think. I realize there's a change in temperature (and internal energy) but I didn't think it was due to heat transfer, only work. So then they claim that Wdone by drill = mCΔT.
I've tried for over an hour to find why they did this, but to no avail. I would appreciate any feedback and the time you take to answer :)
Because no heat is exchanged (because there's no temperature differences between the drill and block), the equation becomes ΔU = 0 + Wdone by drill. But then they confuse me by saying ΔU = Wdone by drill = mCΔT. I am totally confused on why they equate ΔU and W to mCΔT, as mCΔT = Q. Q = 0, so mCΔT would also equal zero I'd think. I realize there's a change in temperature (and internal energy) but I didn't think it was due to heat transfer, only work. So then they claim that Wdone by drill = mCΔT.
I've tried for over an hour to find why they did this, but to no avail. I would appreciate any feedback and the time you take to answer :)