Яндекс.Метрика

Monday, November 9, 2015

Chapter 9. Some Problems from Homework

1) An iceberg is floating in the ocean with 10% of its volume extending above the ocean's surface. What can you say about the iceberg?
a) Its weight is less than the water it displaces.
b) It displaces only 90% of its weight in water.
c) As it melts, a smaller fraction of its volume will extend above the surface.
d) Its density is close to but smaller than the density of water.

2) An ant and an elephant are walking through the jungle. On which does the greater buoyant force act?
a) The ant.
b) The elephant.
c) The same buoyant force acts on both.
d) Neither is floating, so no buoyant force is acting at all.

3) A boat floating in a large pool is loaded with solid iron bars. The water level at the pool's edge is marked with a red line. The iron is now thrown overboard. When the water becomes calm again,
a) the red line is slightly lower than the water level.
b) the red line is slightly higher than the water level.
c) the red line is still at the water level.

4) A clown at the circus blows up a balloon with helium. This balloon will not float to the ceiling unless
a) the pressure of the helium inside the balloon is greater than the atmospheric pressure.
b) the weight of the balloon is less than the weight of the air displaced by the balloon.
c) the balloon and the helium it contains weigh less than the air displaced by the balloon.
d) the pressure of the helium inside the balloon is less than the atmospheric pressure.

5) Suppose a little bubble of air has gotten into the top of a mercury barometer. If a person uses a barometer in the usual way, the reading of atmospheric pressure will be
a) correct.
b) higher than the actual value.
c) lower than the actual value.

6) A uniform wooden plank floats in a swimming pool. The plank weighs 100 pounds, and exactly 10% of its volume is above the waterline. The maximum weight of iron which could be suspended from underneath the plank without causing the whole combination to sink to the bottom of the pool is
a) exactly 10 pounds.
b) somewhat more than 10 pounds.
c) somewhat less than 10 pounds.
d) more information is needed.

7) A block that has a density of 900 kg/m3 is placed in water (density 1000 kg/m3). The block will
a) sink to the bottom.
b) sink until it is almost, but not entirely, submerged.
c) sink until it is entirely submerged and then remain in place just below the surface.
d) sink just a little bit with most of the block above the water.
e) rest on the water with none of the block submerged.

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