Fluids

1. Fluids Physics 152

2. 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 • registers the same increase. • registers a smaller increase. • registers a larger increase.

3. 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? • It rises. • It falls. • It stays the same.

4. 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 • gets pushed down. • stays the same. • moves up.

5. 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? • Towards the front of the car. • Towards the rear of the car.

6. 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) • its volume is about the same. • its volume has increased by about 50%. • its volume has approximately doubled.

7. 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? • About 32% • About 36% • About 40% • About 44%

8. 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? • The ball will be blown away. • The ball will balance above the jet of air. • The ball will be sucked into the funnel.

9. 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? • 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.

10. 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? • Yes • No

11. 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? • It stays there • It moves back up • It moves further down

12. 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? • Same speed • Twice as fast • 4 times faster • 8 times faster

13. Plaque reduces the radius of an artery by 10%. Assuming blood pressure remains constant, blood flow through the artery is reduced by approximately: • One fifth • One quarter • One third • One half

14. 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: • 0.5v • v • 2v • 4v • 8v

15. A coffee filter falls through air at steady speed v. A stack of 4 such filters will fall at speed: • v • 2v • 4v

16. The Reynolds number for airflow around a car traveling down a highway is (very approximately): • 1 • 103 • 106 • 109

17. The Reynolds number for a falling raindrop is (very approximately): • 10-3 • 1 • 103 • 106