posted by Anonymous

What is the sign of heat(Q), Work(W), or Temperature for these following situations. Say if it's +,-, or 0.

1)You hit a nail with a hammer: +W, Q=0, T=0

2)You hold a nail over a Bunsen burner: Q=+Q, Temp:constant, W=0

3)You compress the air in a bicycle pump by pushing down on the handle very rapidly: -W, Temp:-, Q is -.

4)You turn on a flame under a cylinder of gas, and the gas undergoes an isothermal expansion:
isothermal is constant T, +Q, W is +

5)A flame turns liquid water into steam:
+Q,+W,+T

6)High pressure steam spins a turbine:
T inc so +, +Q, +W

7)Steam contacts a cold surface and condenses:
-Q, -W, Temp decreases

Can you check my work and correct me?

1. Damon

2. does the temp of the nail not increase?
3. When you squeeze gas it gets hot. If you do it rapidly enough there is no time for heat to escape.
4. That did the gas do work on?
5. Again I do not see any work being done.
6. The steam expands through the turbine, losing temperature and doing work
7. Again what work is being done?

2. Count Iblis

You have to define what the system is. In case of 1) if I take the system to be the nail, then

W = 0

Q = positive

T = Positive.

By definition, work is the change in itnernal energy due to a change in the external parameters of a system. In case of the nail, the external parameters (like volume) do not change. What happens is that work is performed by the person hammering the nail, but this converted to heat via friction and this heat is delivered to the nail.

The first law for the nail is:

Delta U = Q - W

I.e. internal energy gain of the nail is heat delivered to the nail minus work perfomed by the nail. The latter is zero and the former is positive, so the nail gains in internal energy, which causes the temperature to rise.

## Similar Questions

1. ### Physics warming a nail

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 …
2. ### Physics

The collision between a hammer and a nail can be considered to be approximately elastic. Estimate the kinetic energy acquired by a 13 g nail when it is struck by a 550 g hammer moving with an initial speed of 4.0 m/s. I solved for …
3. ### physical science

A nail is driven into a board to a depth of 1.00 cm with one strike from the hammer. The hammer striking the nail hit it with a force of 200.00 Newtons. How much work was done?
4. ### Physics

A farmer drives a 0.100 kg iron spike with a 2.00 kg sledge hammer. The sledge hammer moves at a constant speed of 3.99 m/s until it comes to rest on the spike after each swing. Assuming all the energy is absorbed by the nail, and …
5. ### physics

The figure below shows a claw hammer being used to pull a nail out of a horizontal board where θ = 32.2°. The mass of the hammer is 1.00 kg. A force of 125 N is exerted horizontally as shown, and the nail does not yet move relative …
6. ### Science

A hammer with a 500-g head exerts an average force of 810n on a nail speed as it drives the nail 4 mm into wall. What was the speed of the hammer head when it hit the nail?
7. ### physics b

A nail driven into a board increases in temperature. If 60% of the kinetic energy delivered by a 1.8 kg hammer with a speed of 7.8 m/s is transformed into heat that flows into the nail and does not flow out, what is the increase in …
8. ### Physics

A nail driven into a board increases in temperature. If we assume that 88.6 % of the kinetic energy delivered by a 2.3-kg hammer with a speed of 7.80 m/s is transformed into heat that flows into the nail and does not flow out, what …
9. ### Physics

Hammering a nail into wood makes it get hotter. Consider a 5-g long, 5-gauge steel nail and a hammer that exerts an average force of 500 N on the nail when it is introduced to a piece of wood. The nail gets warmer each time. Demonstrate …
10. ### Physics

Hammering a nail into wood makes it get hotter. Consider a 5-g long, 5-gauge steel nail and a hammer that exerts an average force of 500 N on the nail when it is introduced to a piece of wood. The nail gets warmer each time. Demonstrate …

More Similar Questions