Which statement below regarding the first law of thermodynamics is most correct?
a. A system can do work externally only if its internal energy decreases.
b. The internal energy of a system that interacts with its environment must change.
c. No matter what other interactions take place, the internal energy must change if a system undergoes a heat transfer.
d. The only changes that can occur in the internal energy of a system are those produced by non-mechanical forces.
e. The internal energy of a system cannot change if the heat transferred to the system is equal to the work done by the system.
e
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In 1020 steel, the only significant element other than iron and carbon is _________.
Fill in the blank(s) with the appropriate word(s).
Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in an orbiting space vehicle do not, because passengers in the space vehicle are
A) beyond the main pull of Earth's gravity. B) above Earth's atmosphere. C) without support forces. D) all of the above E) none of the above
The two masses in the figure are released from rest. After the 3.0-kg mass has fallen 1.5 m, it is moving with a speed of 3.8 m/s. What is the change in mechanical energy done on the system during this time interval by the frictional force on the 2.0 kg mass?
A. ?12 J B. ?17 J C. ?20 J D. ?8.0 J E. ?28 J
Which of the following combinations of variables results in the greatest period for a pendulum?
A.
B.
C.
D.
L, mass = 
M, and maximum angular displacement = 
degreesE.
L, mass = 4M, and maximum angular displacement = 4 degrees