Physics 41 Exam 3 Practice HW
1.A bridge is made with segments of concrete 50 m long. If the linear expansion coefficient is 12 10–6 (°C)–1, how much spacing (in cm) is needed to allow for expansion during an extreme temperature change of 150°F?
a. 10b. 2.5c. 7.5d. 5.0e. 9.5
2.One mole of an ideal gas has a temperature of 25C. If the volume is held constant and the pressure is doubled, the final temperature (in C) will be
a.174 b. 596 c. 50 d. 323 e. 25
3.A bubble having a diameter of 1.00 cm is released from the bottom of a swimming pool where the depth is 5.00 m. What will the diameter of the bubble be when it reaches the surface? The temperature of the water at the surface is 20.0C, whereas it is 15.0C at the bottom. (The density of water is 1.00103kg/m3.)
a.1.05b.1.15c.1.45d. 1.65e. 1.35
4.A 5-kg piece of lead (specific heat 0.03 cal/g °C) having a temperature of 80°C is added to 500 g of water having a temperature of 20°C. What is the final equilibrium temperature (in °C) of the system?
a.79b.26c.54d.34e.20
5.If 25 kg of ice at 0°C is combined with 4 kg of steam at 100°C, what will be the final equilibrium temperature (in °C) of the system?
a.40b.20c.60d.100e.8
6.A child has a temperature of 101°F. If her total cross-sectional area is 2 m2, find the energy lost each second (in W) due to radiation, assuming the emissivity is 1. (Assume the room temperature is 70°F.)
a.217b.180c.90d.68e.850
7.A 5-g coin is dropped from a 300-m building. If it reaches a terminal velocity of 45 m/s, and the rest of the energy is converted to heating the coin, what is the change in temperature (in °C) of the coin? (The specific heat of copper is 387J/kg°C.)
a.9b.2c.5d.21e.0.5
8.Five gas molecules are found to have speeds of 100, 200, 300, 400, and 500 m/s. The rms speed (in m/s) is
a.390.b.300.c.360.d.330.e.320.
9.The air in an automobile engine at 20C is compressed from an initial pressure of 1.0 atm and a volume of 200 cm3 to a volume of 20 cm3. Find the temperature if the air behaves like an ideal gas ( = 1.4) and the compression is adiabatic.
a.730Cb.460Cc.25Cd.50Ce.20C
10.A refrigerator has a coefficient of performance of 4. If the refrigerator absorbs 30cal of heat from the cold reservoir in each cycle, the heat expelled (in cal) into the heat reservoir is
a.40.5b.37.5c.36.5d.34.5e.22.5
11.A lawn mower has a 6-horsepower engine (1 HP = 750 W). If the engine has an efficiency of 20%, and the throttle is such that the engine cycles 10 times a second, the heat that is expelled in one cycle is
a.1800 Jb.2000 Jc.2200 Jd.2400 Je.2250 J
12.An automobile engine operates with an overall efficiency of 12%. How much energy is delivered as waste heat (in gallons of gasoline) for each 10 gallons of fuel burned?
a.1.2b.8.8c.6.5d.4.7e.7.5
Which of these engines can NOT be built? Why? Justify your reasoning for each engine. What laws/theories are violated?
Long Problem:
A heat engine uses a diatomic gas that follows the PV cycle shown.
a. Determine the pressure, volume and temperature at point 2.
b. Determine Eint, W and Q for each of the three processes.
Put your results in a table for easy reading
c. How much work does this engine do per cycle and what is its thermal efficiency?
You Should also do Problems 15 and 34 from Chapter 22