Determine the change in thermal energy of a 30 kg wooden bench that warms from 15oC to 25oC if the specific heat of wood is 1,700 J/(kgoC). Show formula and work.

Question

Determine the change in thermal energy of a 30 kg wooden bench that warms from 15oC to 25oC if the specific heat of wood is 1,700 J/(kgoC).  Show formula and work.

anonymous · Answer

Is it ?
Q = m(Tf - Ti)C
Q = 30kg(15C-25C)1,700 J/(kgC)
Q = -510,000 ?

jamesj · Answer

Doesn't the energy have to go up?

anonymous · Answer

Yeah ?

jamesj · Answer

So the answer should be positive.  Check your signs.

anonymous · Answer

It should be 510,000 J ?

jamesj · Answer

Yes.  Tf = 25 and Ti = 15, hence
Tf - Ti = +10, not -10

jamesj · Answer

Always sense check your answers in Physics.  Ask yourself what the answer means and whether it is consistent with what you're trying to do.

anonymous · Answer

Thanks again . :)