Superguy is flying at treetop level near Paris when he sees the Eiffel Tower elevator start to fall (the cable snapped). His x-ray vision tells him Lois LaTour is inside. If Superguy is 1.00 km away from the tower, and the elevator falls from a height of 2.1 × 10^2 m, how long does Superguy have to save Lois, and what must be his average speed?
a. 4.5 s, 200 m/s
c. 7.0 s, 140 m/s
b. 6.5 s, 150 m/s
d. 9.0 s, 110 m/s
B
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The rigid object shown is rotated about an axis perpendicular to the paper and through point P. The total kinetic energy of the object as it rotates is equal to 1.4 J. If M = 1.3 kg and L = 0.50 m, what is the angular velocity of the object? Neglect the mass of the connecting rods and treat the masses as particles.
A. 1.3 rad/s B. 1.5 rad/s C. 1.7 rad/s D. 1.2 rad/s E. 2.1 rad/s
The tiny ripples in the background radiation COBE found are due to
A) bubble-like nature of space. B) reddening by interstellar dust clouds in our galaxy. C) a gravitational redshift caused by growing dark clumps. D) variations in the speed of different wavelengths of light. E) different velocities of the edge of the universe.
An ideal Carnot engine operates between reservoirs having temperatures of 125°C and -20°C. Each cycle the heat expelled by this engine is used to melt 30.0 g of ice at 0.00°C
The heat of fusion of water is 3.34 × 105 J/kg and the heat of vaporization of water is 2.25 × 106 J/kg. (a) How much work does this engine do each cycle? (b) How much heat per cycle does this engine absorb at the hot reservoir?
Suppose that we allowed each person 1000 m3 of living space in a large building, with ceiling height 3 m
To the nearest order of magnitude, how many 1000 m high buildings would have to be built to house the entire population of 8.5 x 1014 people on the energy-limited Earth if each building's base were 100 km on a side? a. 101 b. 102 c. 105 d. 108 e. 1013