Resistance and Resistivity: A 120-m long metal wire having a resistivity of 1.68 × 10-8 ? ? m has a resistance of 6.0 ?. What is the diameter of the wire?
A. 0.065 mm
B. 0.65 mm
C. 0.65 cm
D. 0.65 m
Answer: B
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The force of gravity is the only one of the four forces felt on very large size scales. Which of the following best explains why the other forces don't play a major role on large scales?
A) The other three forces are all very short in range, and cannot be felt over large distances. B) The strong and weak forces act only on very small scales, and large objects tend to be electrically neutral and therefore don't feel an electromagnetic force. C) Gravity is by far the strongest force, so it simply dominates on large size scales. D) Effects of the strong and weak forces tend to cancel out effects of the electromagnetic force on large scales.
A figure skater on ice with arms extended, spins at a rate of 3.5 rev/s. After he draws his arms in, he spins at 6.0 rev/s. By what factor does the skater's kinetic energy change when he draws his arms in?
a. 2.4 b. 1.7 c. 0.58 d. 0.12
According to the Big Bang model, in the earlier state of the Universe gamma rays converted into ________.
A. hydrogen and helium B. pairs of matter and antimatter C. pairs of protons and neutrons D. X-rays
A very lightweight horizontal loop of wire is suspended from a fine spring, lowered into water, and then raised to the surface. Any further attempt to raise it causes the spring to
A) stretch. B) contract. C) stay the same.