Fluids
Physics 152
A piece of iron hanging on a string is lowered into a beaker
of water on a spring scale, the water level reaches the top
of the beaker and the scale registers an increase. If instead
you immerse your hand so the water level reaches the top,
the scale
1.
2.
3.
registers the same
increase.
registers a smaller
increase.
registers a larger
increase.
You are sitting in a rowing boat in a small pond. There are
some bricks in the boat. You take the bricks and throw
them into the pond. They sink to the bottom.
What happens to the water level in the pond?
1.
2.
3.
It rises.
It falls.
It stays the same.
A ball is floating partially immersed in water. A layer of oil is
poured on top of the water. Relative to the level of the top
surface of the water, the ball
1.
2.
3.
gets pushed down.
stays the same.
moves up.
A car is moving at steady velocity down the highway.
Inside, a helium filled balloon rests lightly against the roof.
Suddenly the car accelerates. This causes the balloon to
move. Which way?
1.
2.
Towards the front of the
car.
Towards the rear of the
car.
A diver is sixty feet below the water surface. A bubble
about one inch radius leaves his breathing apparatus and
travels upwards. When it is at a depth of thirty feet, halfway
to the surface (and assuming bubble temperature constant)
1.
2.
3.
its volume is about the
same.
its volume has
increased by about
50%.
its volume has
approximately doubled.
If you go up from sea level to 2000 meters altitude, the atmospheric
pressure drops by about 20%. How much does it drop if you go from
sea level to 4000 meters altitude?
1.
2.
3.
4.
About 32%
About 36%
About 40%
About 44%
A vertically held funnel has the narrow part down. An air
supply is connected to the narrow low end, and a strong
current of air blown through. A light ball is pushed into the
wide part of the funnel, then let go. What happens?
1.
2.
3.
The ball will be blown
away.
The ball will balance
above the jet of air.
The ball will be sucked
into the funnel.
I suspend two sheets of paper from my hands, so the
sheets are parallel and about 2 cm apart. I blow between
them. How do they move?
1.
2.
3.
They swing apart to
some extent.
They wave around, but
on average stay the
same distance apart as
when the air was still.
They move towards
each other.
A styrofoam cup filled with water has two holes in the
sides, which I block with my fingers. I drop the cup. As it
falls, does water leak out through the holes?
1.
2.
Yes
No
A partly inflated rubber balloon tied to a small weight is in
neutral equilibrium motionless fully submerged one meter
below the surface of a quiet lake. I push it down a few
centimeters, then leave it. What happens?
1.
2.
3.
It stays there
It moves back up
It moves further down
Two rivers flow smoothly down the same incline. One river
is twice as deep as the other. How much faster is the
current on the surface of the deeper river?
1.
2.
3.
4.
Same speed
Twice as fast
4 times faster
8 times faster
Plaque reduces the radius of an artery by 10%. Assuming
blood pressure remains constant, blood flow through the
artery is reduced by approximately:
1.
2.
3.
4.
One fifth
One quarter
One third
One half
A tiny steel ball falls through glycerin at steady speed v.
A similar ball having twice the radius will fall through the
glycerin at speed:
1.
2.
3.
4.
5.
0.5v
v
2v
4v
8v
A coffee filter falls through air at steady speed v.
A stack of 4 such filters will fall at speed:
1. v
2. 2v
3. 4v
The Reynolds number for airflow around a car
traveling down a highway is (very approximately):
1.
2.
3.
4.
1
103
106
109
The Reynolds number for a falling raindrop is (very
approximately):
1.
2.
3.
4.
10-3
1
103
106