A figure skater is spinning slowly with arms outstretched. She brings her arms in close to her body and her moment of inertia decreases by 1/2. By what factor does her rotational kinetic energy change?
A) 2
B) 4
C)
D) 1/2
E) It doesn't change.
A
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Fireworks go off at the same time according to Earth clocks in two cities, Alum and Boron, that are 300 km apart. The people in a spaceship that is flying in a straight line from Alum to Boron at 0.80c also observe the fireworks. Do they see the fireworks in the two cities simultaneously? If the people in the spaceship say the fireworks were not simultaneous in Alum and Boron, how long before or after the fireworks flashed at Alum did the fireworks flash at Boron according to their calculations? (The spaceship is directly over Alum when the fireworks flash.)
A. Yes; 0 B. Before; 1.0 × 10?3 s C. After; 1.0 × 10?3 s D. Before; 1.3 × 10?3 s E. After; 1.3 × 10?3 s
When did humans first learn that Earth is not the center of the universe?
A) about 2000 years ago B) around the time that early humans acquired language C) within the past 500 years D) We haven't; there is still considerable scientific debate about whether Earth is the center of the universe.
A source emits sound at a fixed constant frequency f.If the source moves away from you faster than the speed of sound in air, the frequency that you hear is
a. the same as f. b. higher than f. c. lower than f. d. unrelated to f.
Mechanization of southern agriculture was responsible for the increase in northern African-American populations
What will be an ideal response?