AP Physics – Hewitt Next Time Questions – Fluids
1. Consider a boat loaded with scrap iron in a
swimming pool. If the iron is thrown overboard
into the pool, will the water level at the edge of the
pool rise, fall, or remain unchanged?
Explain your answer in detail!
2. A block of balsa wood with a rock tied to it floats in water.
When the rock is on top as shown, exactly half the block is
below the water line.
When the block is turned over so the rock is underneath and
submerged, the amount of block below the water line is
a) less than half
b) half
c) more than half
and the water level at the side of the container will
d) rise
e) fall
f) remain unchanged
Explain your answers,
Name__________________________________
3. In the presence of air, the small iron ball and large plastic ball
balance each other. When air is evacuated from the container,
the larger ball
a) rises
b) falls
c) remains in place
Explain your answer.
4. An astronaut on earth notes that in her soft drink an ice cube floats with 9/10 its
volume submerged. If she were instead in a lunar module parked on the moon, the
ice in the same soft drink would float with
a) less than 9/10 submerged.
b) 9/10 submerged.
c) more than 9/10 submerged.
Explain your answer.
5. The density of the block of wood floating in water is
a) greater than the density of water
b) equal to the density of water
c) less than half that of water
d) more than half the density of water
e) .. . not enough information is given.
Explain your answer.
6. Consider a Ping-Pong ball floating in a glass of water that is enclosed in an
airtight chamber.
When air pressure is increased in the chamber, does the ball float lower,
higher, or as before?
7. Consider an air-filled balloon weighted so that it is on the verge of sinking ...
that is, its overall density just equals that of water. Now if you push it
beneath the surface, it will
a) sink
b) return to the surface
c) stay at the depth to which it is pushed.
Explain your answer.
8. Compared to an empty ship, will a ship loaded with a
cargo of styrofoam float lower in water or higher in
water?
9. The weight of the stand and suspended solid
iron ball is equal to the weight of the container
of water as shown above. When the ball is
lowered into the water, the balance is upset.
The amount of weight that must be added to the
left side to restore balance, compared to the
weight of water displaced by the ball, would be
a) half
b) the same
c) twice
d) more than twice
Explain your answer.
10. A fire truck carrying a load of fire fighters and a large
tank of water is about to cross a bridge that may not
support the load. The chief suggests that some of the
people aboard get into the tank so the load will be less.
Is this a good idea or a poor idea? Explain.
11. If you release a ball inside a freely-falling
elevator it stays in front of you instead of
"falling to the floor" because you, the ball, and
the elevator are all accelerating downward at
the same acceleration, g. If you similarly
release a helium-filled balloon, the balloon will
a) also stay in front of you
b) press against the ceiling
c) press against the floor
Explain your answer.
12. The inverted drinking glass filled with air is placed mouth downward in water. As it is
pushed deeper, the air is compressed. How deep must the glass be pushed in order that the
air be compressed to half its original volume?
At this depth, how will the buoyant force on the submerged glass compare to when it was
submerged at the surface? Show your work/Explain.
13. Everybody knows that 'water seeks its own level' but very few people know
why water seeks its own level. The reason has most to do with
a) atmospheric pressure,
b) water pressure depending on depth,
c) water's density.
Explain.
14. An ice cube floats in a glass of water that is “brim full”. When the ice cube melts,
a) the water will overflow the glass
b) the water level will remain the same
c) the water level will go down
Explain.
15. Gently push down on the pan of the scale and the display shows an increase in
force. Likewise if you do the same on the rim of the beaker. But what if you
immerse your fingertip in the water without touching the beaker? Then the
scale reading
a) doesn’t change
b) shows an increase
c) shows a decrease.
16. Buoyant force is greater in an empty ship when it is
a) floating on the surface
b) capsized and sitting on the bottom
c) Same either way
Buoyant force is greater on a submarine when it is
d) floating.
e) submerged
f) same either way
17. Suppose that the part of an iceberg that extends above
the water were suddenly removed. If this occurred, the
a) center of mass of the iceberg would sink slightly
b) buoyant force on the iceberg would decrease
c) density of the iceberg would slightly decrease
d) pressure at the bottom of the iceberg would increase
e) Two of these answers are correct
f) All are incorrect
Explain.
18.
19. Compared with the weight of a soccer ball or a baseball, the weight of air
in an “empty” refrigerator is
a. negligible
b. about 1/4/ as much.
c. about the same.
d. more.
Explain your answer.
20. A block of wood and a block of iron on weighing scales
each weigh 1 ton. Strictly speaking, which has the greater
mass? Explain!
21. A birthday candle burns in a deep drinking class. when the glass is whirled around in a
circular path, say held at arm’s length while one is spinning like an ice skater, which way
does the candle flame point? Explain your answer.
22. Water with air bubbles flows through a pipe that gets
narrower. In the narrow region the water gains speed and
the bubbles are:
Explain your answer?
23. You’re driving in a convertible car with the top up and the
windows closed. You note that the fabric top puffs up. To
explain this interesting phenomenon, you invoke
a. Bernoulli’s principle
b. Newton’s laws
c. Both
Explain your answer