Physics 73 1st Exam Review

Physics 73

st 1

Exam Review

Question 1 (3 mins) •

A 1.3 kg sample of copper (c = 0.389 kJ/kg⋅K) was heated to 100○C and placed in a container filled with 500 mL of water with temperature 20○C. What is the final temperature of the system? A. B. C. D.

100 ○C 20 ○C 35 ○C 60 ○C

Question 2 (3 mins) •

1.00 kg of ice at 0.00°C and 1.00 kg of steam at 100°C were put in a thermally insulated vessel and was allowed to attain thermal equilibrium. What is the final temperature of the system? A. B. C. D.

0.00°C 50.0°C 100°C 279°C

Question 3 (1 min) •

Which of the following is an assumption of the kinetic molecular theory? A. The size of gas particles is comparable to the container dimensions. B. Gas particles undergo inelastic collisions with the container walls.

C. The gas particles obey Newton’s laws of motion. D. The gas molecules can lose energy due to collisions and eventually come to rest.

Question 4 (2 mins.) •

What is the fraction of He atoms with speeds above 1368m/s if the temperature is 300K ? The molar mass of Helium is 4.00 grams/mole. A. 0.608 B. 0.218 C. 0.077 D. 0.392

v/vrms   fractio n 0.011 0.20 0.077 0.40 0.218 0.60 0.411 0.80 1.00 0.608

v/vrms   fractio n 1.20 0.771 1.40 0.882 1.60 0.947 1.80 0.979 2.00 0.993

Question 5 (2 mins.) •

A cylinder fitted with a piston contains 0.10 mol of air at room temperature (20°C). The piston is pushed slowly so that the air within the cylinder remains essentially in thermal equilibrium with the surroundings. What is the work done by the air within the cylinder if the final volume is one-half the initial volume?

A. B. C. D.

-169 J +169 J -576 J +576 J

Question 6 (1 min.) •

An ideal gas changes its state reversibly from A to C. Which of the following is true about the change of internal energy of the gas?

A. Greatest for process A →C B. Greatest for process A →B→C C. Greatest for process A →D→C D. Least for process A → C E. The same for all three paths

Question 7 (4 mins.) •

A cycle of an engine that uses a diatomic gas as its working substance is shown by the figure. What is the efficiency of this engine if  =    = 600 ,  = 1800  ,   = 200  ?

A. 84.6 % B. 23.1 % C. 0 % D. 15.4 %

Question 8 ( 3 mins.) •

Consider the hypothetical setup below. An engine with an efficiency of 0.250 is used by a refrigerator with a COP of 3.50. If the engine uses 100 kJ per cycle to operate, how much heat can the refrigerator remove from its cold reservoir per cycle?

A. 87.5 kJ

B. 350 kJ

A. 27.5 kJ

A. 75.0 kJ

Question 9 (1.5 mins.) •

1.51 kg of steam condensed into liquid water at 100 °C. Compute its change in entropy. A. -9.13 kJ/K

B. +9.13 kJ/K C. -34.07 kJ/K D. 0 kJ/K

Question 10 (2 mins.) •

Consider ten coins. Macrostate 1 consists of nine heads and one tail. Macrostate 2 consists of nine tails and one head. What is the change in entropy from macrostate 1 to macrostate 2? A.

   ln 10

B.

  −ln9

C.

  ln9

D.

0