2.) Pounding a nail into wood makes the nail warmer. Consider a 5-g steel nail 6 cm long and a hammer that exerts an average force of 500 N on the nail when it is being driven into a piece of wood. The nail becomes hotter. Show that the increase in the nail's temperature is 13.3oC. (Assume the specific heat capacity of steel is 450 J/kg*oC.)

Question

I used the formula Q = cm(change in temp)
to get (Q being quantity of heat):
Q = 450J/kg(5g)13.3oC
I'm not sure where the 500N or 6cm come in.

Answer 1

Force x distance = Work, and most of that work ends up as heat in the nail. (Actually, the wood heats up also, but they want you to neglect that because the heat does not travel far into the wood right away, although eventually it does).

Your equation for Q is not correct. They want you to compute Q from the force and nail length, and then use the heat capacity C o get the temperature change.

Q = 500 N x 0.06 m = 30 J
temperaure rise = Q/(M C)
= 30 J/[(.005kg)*(450J/kg C)]= __ C

Answer 2

Thanks so much! Now it makes sense. I still have a question, though. Why did you change the gm to kg? I wanted to know so that I would know when to convert. Thank you - Mary :-)