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Chapter 1: Q6DQ (page 389)
In hot-air ballooning, a large balloon is filled with air heated by a gas burner at the bottom. Why must the air be heated? How does the balloonist control ascent and descent?
The balloon is filled with air heated because warm air is less dense as compared to cold air.
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A closed and elevated vertical cylindrical tank with diameter 2.00 m contains water to a depth of 0.800 m. A worker accidently pokes a circular hole with diameter 0.0200 m in the bottom of the tank. As the water drains from the tank, compressed air above the water in the tank maintains a gauge pressure of 5 X 103Pa at the surface of the water. Ignore any effects of viscosity. (a) Just after the hole is made, what is the speed of the water as it emerges from the hole? What is the ratio of this speed to the efflux speed if the top of the tank is open to the air? (b) How much time does it take for all the water to drain from the tank? What is the ratio of this time to the time it takes for the tank to drain if the top of the tank is open to the air?
A rubber hose is attached to a funnel, and the free end is bent around to point upward. When water is poured into the funnel, it rises in the hose to the same level as in the funnel, even though the funnel has a lot more water in it than the hose does. Why? What supports the extra weight of the water in the funnel?
You are on the roof of the physics building, above the ground (Fig. P2.70). Your physics professor, who istall, is walking alongside the building at a constant speed of. If you wish to drop an egg on your professor’s head, where should the professor be when you release the egg? Assume that the egg is in free fall.
(Fig. P2.70)
You have probably noticed that the lower the tire pressure, the larger the contact area between the tire and the road. Why?
In 2005 astronomers announced the discovery of large black hole in the galaxy Markarian 766 having clumps of matter orbiting around once every and moving at . (a) How far these clumps from the center of the black hole? (b) What is the mass of this black hole, assuming circular orbits? Express your answer in kilogram and as a multiple of sun’s mass. (c) What is the radius of event horizon?
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