1. A large copper tank is 3 m long when it’s at room temperature 20 oC....

1. A large copper tank is 3 m long when it’s at room temperature 20 oC. When the tank is partially filled with hot water, its temperature rises to 95 oC. What is the length of the copper tank at this temperature? The coefficient of linear expansion for copper is 17×10-6 /oC. (5pts)

2. When you press on the brake pedal of a car the car slows down. This means that the car’s kinetic energy decreases. You might ask where does that KE go? The answer is into heat and therefore the brakes get hot. Let’s assume that the brake mechanism for the car is made of steel and the total mass of the brakes is 20 kg. (Steel has a specific heat capacity of 460 J/(kg oC).)

(a) A car with mass 1,000 kg is moving at 20 m/s. What is the kinetic energy of the car? (5 pts)

(b) The car stops with its brakes, and the KE is transferred to heat in the brakes. By how much does the temperature rise inside the brakes? (5pts)

3. Concrete has a coefficient of linear expansion of about 8 × 10-6/°C. If you were to build a bridge from concrete panels, you would have to leave a gap between them so that the concrete panels would have room to expand on a hot day. Suppose you leave a gap of 1.5 cm between panels, and you require that the panels must expand by only 1.3 cm when the temperature rises by 60 °C. What is the maximum length of the concrete panels? (5 pts) 1

5. Here’s some data on thermal conductivity for various materials (the units are W/(m°C): aluminum: k = 237 copper: k = 400 iron: k = 72 If you had to select between kettles made of aluminum, copper and iron for boiling water on a stove top, which kettle type should you choose? (5 pts)

6. A 10 kg block of iron is dropped into a 10 kg pool of water. The temperature of the iron is initially 100 °C, and the temperature of the water is initially 20 °C. Circle all the statements that are true. (5 pts)

a. Heat moves from the iron into the water.

b. Heat moves from the water into the iron.

c. Heat moves so that the heat in the iron is equal to the heat in the water.

d. Heat moves so that the final temperature of the iron and water are equal.

e. The final temperature of the water and iron will be greater than 20°C and less than 100 °C.

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Expert Solution

genius_generous answered 1 year ago

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