Perfect heat powered engine, my TA says:

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A perfect heat engine, theoretically 100% efficient, would convert all heat energy into mechanical energy, meaning the output would equal the input. However, such an engine is impossible according to the laws of thermodynamics. The maximum efficiency of any heat engine is determined by the temperatures of its heat source and sink, expressed as (Th-Tc)/Th. Therefore, the statement about achieving perfect efficiency is inaccurate. In reality, no engine can achieve 100% efficiency due to inherent energy losses.
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my TA in my physics class told us that if there was a perfect engine powered by heat (100% efficent) then the mechanical energy generated by the engine would be the same as the amount of heat energy used by the engine. I am not sure what he is getting at here, or trying to say by this, but is this even accurate?
 
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wakejosh said:
my TA in my physics class told us that if there was a perfect engine powered by heat (100% efficent) then the mechanical energy generated by the engine would be the same as the amount of heat energy used by the engine. I am not sure what he is getting at here, or trying to say by this, but is this even accurate?
This is true, if we were able to build a 100% efficient heat engine (which itself is theoretically impossible), then any heat we put into the engine could be used to do work.
 
wakejosh said:
my TA in my physics class told us that if there was a perfect engine powered by heat (100% efficent) then the mechanical energy generated by the engine would be the same as the amount of heat energy used by the engine. I am not sure what he is getting at here, or trying to say by this, but is this even accurate?
Following on what Hootenanny said, which is quite correct, I would prefer to say that this statement is not accurate. A perfect heat engine can not be 100% efficient. It can, at most be Th-Tc/Th efficient where Tc and Th are the temperatures that it operates between.

AM
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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