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
c. 0.58
b. 1.7
d. 0.12
B
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An aluminum tube (E 5 72 GPa) AB of circular cross section has a pinned support at the base and is pin-connected at the top to a horizon-tal beam supporting a load Q 5 600 kN. The outside diameter of the tube is 200 mm and the desired factor of safety with respect to Euler buck-ling is 3.0. The required thickness t of the tube is most nearly:
(A) 8 mm
(B) 10 mm
(C) 12 mm
(D) 14 mm
A turbine takes in 2 200-K steam and exhausts the steam at a temperature of 200 K. What is the maximum theoretical efficiency of this system?
a. 83% b. 75% c. 91% d. 68% e. 62%
A person walks in a distance x northward, turns around and walks a distance 7.00x southward. If the total displacement of the person from his starting position is 400 m south. What was the total distance walked?
A) 421 m B) 457 m C) 515 m D) 533 m E) 400 m
If a wave from one slit of a Young's double-slit set-up arrives at a point on the screen one-half wavelength behind the wave from the other slit, what is observed at that point?
a. dark fringe c. gray fringe, neither dark nor bright b. bright fringe d. multi-colored fringe