When an ice skater twirling on the point of a skate draws her arms in she ends up whirling faster. This is because
A. linear momentum is conserved.
B. angular momentum is conserved.
C. rotational energy is conserved.
D. a net external torque acts on the skater.
Answer: B
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The mass of Mars, 6.40 × 1023 kg, is about one-tenth that of Earth, and its radius, 3395 km, is about half that of Earth. What is the mean density (mass divided by volume) of Mars in kilograms per cubic meter?
A) 9.76 × 102 kg/m3 B) 1.95 × 103 kg/m3 C) 3.90 × 103 kg/m3 D) 7.81 × 103 kg/m3
Polarization involves
a. the orientation of field vectors. b. only longitudinal waves. c. diffraction. d. interference.
Suppose there are 3 molecules in a container. If each molecule has a 1-in-2 chance of being in the left half of the container, what is the probability that there are exactly 2 molecules in the left half of the container?
a. 1/2 b. 1/3 c. 1/8 d. 3/8 e. 3/5
If R = 3.0 k?, C = 6.0 nF, ?1 = 10.0 V, Q = 18 nC, ?2 = 6.0 V, and I = 5.0 mA, what is the potential difference Vb?Va?
A. ?13 V B. +28 V C. +13 V D. ?28 V E. +2.0 V