Phy 101 Test 3

The reason fast-moving water makes noise is A. lift. B. turbulence. C. laminar flow. D. chaos.

Turbulence

The onset of turbulent flow happens for a Reynolds number of about A. 2300 B. 5000 C. 0 D. Infinity

2300

Gravity creates A. lack of pressure on the top of all fluids. B. constant motion in fluids. C. uniform pressure in fluids. D. Gravity creates

Gravity creates

At what place in or near the jet engine is gas moving the fastest relative to the flying airplane? A. In the plume of exhaust gas flowing out of the engine's outlet duct. B. In the air flowing into the engine's inlet duct. C. In the engine's turbine section. D. In the engine's compressor section.

In the plume of exhaust gas flowing out of the engine's outlet duct.

Lead sinkers actually float on the surface of liquid mercury. Which takes up more space: 1 kg of mercury or 1 kg of lead? A. Mercury B. Neither take up any space C. Not enough information is given D. Lead

Lead

For an object that sinks in a fluid, A. The weight of fluid displaced is less than its weight. B. The weight of the fluid displaced is greater than the object's weight. C. The weight of the fluid displaced equals the object's weight. D. The weight of the object becomes more than in air.

The weight of fluid displaced is less than its weight.

Cities have to use water towers to supply water to because A. Water pressure at the bottom of the tower is much higher than at the top. B. The water tower has a vault of air that is pressurized. C. Water moves fastest at the bottom of the water tower and this speed is transmitted uniformly throughout all water pipes below. D. Water pressure at the top of the tower is transmitted through the water pipes.

Water pressure at the bottom of the tower is much higher than at the top.

On a windy day you notice that a tall light pole is bent away from its equilibrium position. If the wind speed were to increase the pole would A. remain bent by the same amount because the larger drag force will be canceled by a larger restoring force. B. straighten out because the airflow would become laminar and reduce the drag force. C. remain bent by the same amount since aerodynamic drag forces, like sliding friction, are independent of the relative speed of the objects. D. bend further from its equilibrium position because the aerodynamic drag forces that are bending the pole will increase with the speed of the air moving around the pole.

bend further from its equilibrium position because the aerodynamic drag forces that are bending the pole will increase with the speed of the air moving around the pole.

As the Reynolds number increases, A. flow is becoming more laminar. B. flow is slowing down. C. flow is going from being viscous dominated to inertia dominated and therefore turbulent. D. flow is speeding up.

flow is going from being viscous dominated to inertia dominated and therefore turbulent

You stop for a cappuccino at a coffee shop and notice that the tiny white bubbles of steamed milk remain on the surface of the coffee. These air-filled bubbles stay where they are, rather than descending into the coffee or rising into the air, because they are A. lighter than the cup of coffee but heavier than the column of air above the coffee. B. thicker than the coffee but less thick than the air above the coffee. C. more dense than the coffee but less dense than the air above the coffee. D. less dense than the coffee but more dense than the air above the coffee.

less dense than the coffee but more dense than the air above the coffee.

A curve ball in baseball curves because of A. drag forces. B. gravitational forces. C. buoyant forces. D. lift forces.

lift forces

You are caulking a window. The caulk is rather thick and, to lay the bead correctly, the exit nozzle is small. A caulking gun uses a plunger which is operated by pulling back on a handle. You must squeeze the handle very hard to get the caulk to come out of the narrow opening because A. viscous drag between the walls of the tip and the caulk causes the caulk to swirl around chaotically. B. pressure is distributed uniformly throughout the fluid and the area of the plunger is much larger than the area of the opening. C. the high density of the caulk impedes its flow through the small opening. D. Newton's third law requires most of the energy in the caulk to be used to push back on the plunger rather than moving it through the tip.

pressure is distributed uniformly throughout the fluid and the area of the plunger is much larger than the area of the opening.

Dimples on a golf ball hit without spin A. reduce drag. B. are merely decorative. C. result in purely laminar flow. D. increase drag.

reduce drag.

Fluids have viscosity because A. they are always in contact with some boundary. B. molecules in fluids are long and get tangled. C. the atoms and molecules within the fluid are heavy and hard to push. D. the atoms and molecules within the fluid interact with each other, producing internal frictional forces.

the atoms and molecules within the fluid interact with each other, producing internal frictional forces.

A squirt gun is a simple type of water pump in which a plunger attached to the trigger forces water out of a nozzle and across the room. When you squeeze the trigger of the gun, water squirts out of the nozzle because A. the Bernoulli effect causes the pressure of water leaving the nozzle to be less than atmospheric pressure. B. the water is compressed at the plunger so it must expand out the nozzle. C. the pressure inside the gun is higher than atmospheric pressure. D. the Bernoulli effect causes the water's overall energy to increase as it travels through the narrow nozzle.

the pressure inside the gun is higher than atmospheric pressure.

Suppose you have an aquarium and you notice that you have a solid plastic decoration and a rock of about the same mass but the decoration is twice as large as the rock. Both are totally submerged in the water. The buoyant force on the plastic object is about ___________as that on the rock. A. twice as big B. one quarter as big C. the same D. half as big

twice as big

In a popular classroom demonstration, a cotton ball is placed in the bottom of a strong test tube. A plunger fits inside the tube and it makes an air-tight seal. It is then pushed down very rapidly, and the cotton flashes and burns. This happens because A. cotton contains a pressure-sensitive substance that burns upon impact. B. it's one of those demos that nobody understands. C. friction between the plunger and the tube ignited the cotton D. when the air was compressed its temperature increased.

when the air was compressed its temperature increased.

Tennis ball A is dry and fuzzy. Tennis ball B is wet, and the fuzz is matted down. What will happen when the two balls are hit horizontally so as to have the same initial horizontal velocity? A. B goes farther than A due to the extra weight of the water. B. B goes farther than A due to the smoother surface. C. Both go the same distance. D. A goes farther than B because the fuzz reduces drag.

A goes farther than B because the fuzz reduces drag.

Aerodynamic forces consist of A. drag and gravity. B. lift and drop. C. drag and lift. D. drag, lift, and buoyancy.

Drag and lift

Pressure potential energy A. Has to do with describing moving water and is only an abstract concept. B. Can be stored for long periods of time to be transported and used. C. Exists only in stationary fluids. D. Has units of pressure.

Has to do with describing moving water and is only an abstract concept.

When a fluid is in steady-state flow and its path bends, the pressure on the outside of the bend is always A. Lower than the pressure on the inside of the bend. B. Infinite. C. Higher than the pressure on the inside of the bend. D. Equal to the pressure everywhere else in the fluid.

Higher than the pressure on the inside of the bend.

Flowing honey is less likely to become turbulent than flowing water because A. water's large pressure favors turbulent flow. B. water's large viscosity favors turbulent flow. C. honey's large viscosity favors laminar flow. D. honey's large density favors laminar flow.

Honey's large viscosity favors laminar flow.

You have just set up a weather station for your daughter to observe wind speeds at home. You had to move it up from the ground because when it was too close to the ground the wind speed readings are all too small. This is because A. The boundary layer of a moving fluid moves slower than at other points farther into the fluid. B. Someone kept stepping on the wind speed gauge. C. The air near the ground is too dense to move well. D. The ground is hot so air movement there is always upward, never sideways.

The boundary layer of a moving fluid moves slower than at other points farther into the fluid.

Why does fuzz on a tennis ball help it travel farther when hit? A. The fuzz causes laminar flow everywhere. B. The fuzz causes turbulence on the trailing edge of the ball only. C. The fuzz causes turbulence on the leading edge of the ball only. D. The fuzz "trips" the boundary layer, causing turbulence everywhere around the ball.

The fuzz "trips" the boundary layer, causing turbulence everywhere around the ball.

For an object that is floating on a fluid, A. The weight of the object becomes less than in air. B. The weight of fluid displaced is less than its weight. C. The weight of the fluid displaced is greater than the object's weight. D. The weight of the fluid displaced equals the object's weight.

The weight of the fluid displaced equals the object's weight.

Suppose that we are able to send astronauts to Mars and they engage in a game of golf on the red planet's surface. Given that the atmosphere on Mars is considerably less dense than our own, how will the path of the ball be affected? A. Less atmosphere means lower gravity, so it will go further than if there were air. B. There is less lift, so the ball doesn't go as far than if there were air. C. There is less drag and gravity, so the ball will go further than if there were air. D. There is no significant effect.

There is less drag and gravity, so the ball will go further than if there were air.

Why are failures in dams more likely to occur closer to the bottom of the dam? A. The temperature is higher at the bottom. B. Water weighs more at the bottom. C. Water is considerably more dense at the bottom. D. Water pressure is higher at the bottom.

Water pressure is higher at the bottom.

Suppose you had a very long straw that could reach from a cup of water on the ground level to the top of a very tall building. When you suck on the straw in order to bring water up, A. You could drink the water at any height with no problem. B. Water is too thick to be pulled up in the straw by more than a few inches. C. You could bring the water up to only a certain height in the straw because after it will flash freeze in the cup. D. You could bring the water up to only a certain height in the straw because the atmosphere pushes down on the surface of the water by a given amount.

You could bring the water up to only a certain height in the straw because the atmosphere pushes down on the surface of the water by a given amount.

Your apartment window opens 20 meters (65 feet) above a lemonade stand. Your friend lowers a long plastic tube out the window until its end enters the tank of delicious lemonade far below. She then begins to suck on the other end of the tube in hopes of getting a free drink. To her dismay, she never tastes a drop because A. the tube has an average density that is larger than that of lemonade, so the buoyant force cannot support its weight. B. the tube's acceleration is downward, so it prevents the lemonade's velocity from being upward. C. lemonade is too thick to pass through a tube that long. D. atmospheric pressure cannot support a column of lemonade 20 meters tall.

atmospheric pressure cannot support a column of lemonade 20 meters tall.

You are taking a shower in your dormitory when someone flushes a toilet nearby. The pressure in the cold water line drops and you find yourself showering in what feels like molten lava. This loss of cold water pressure occurs when the toilet lets cold water flow through the pipes delivering it to the bathroom and the water's speed in those pipes increases. Assuming all the piping to be about on the same level, the cold water's faster motion in the delivery pipes reduces its pressure in the shower head because faster moving water A. losses more energy to viscous drag as it flows through the delivery pipes. B. has less gravitational potential energy than slower moving water. C. has less pressure than slower moving water. D. has less kinetic energy than slower moving water.

has less pressure than slower moving water.

When a Frisbee is flying horizontally through the air, the speed of the air flowing over the Frisbee's top is A. lower than the speed of the air beneath it and the pressure on top of the Frisbee is less than the pressure beneath it. B. higher than the speed of the air beneath it and the pressure on top of the Frisbee is greater than the pressure beneath it. C. higher than the speed of the air beneath it and the pressure on top of the Frisbee is less than the pressure beneath it. D. lower than the speed of the air beneath it and the pressure on top of the Frisbee is greater than the pressure beneath it.

higher than the speed of the air beneath it and the pressure on top of the Frisbee is less than the pressure beneath it.

When you blow on a pinwheel, it starts to spin. Even when you aim the air directly toward the wheel's pivot you produce a torque on the wing-like blades and they undergo angular acceleration. This torque is produced by A. the buoyant force due to the high-pressure air hitting the blades of the pinwheel. B. lift forces on the pinwheel's blades. C. drag forces on the pinwheel's blades. D. a deflection of the air stream directly away from the pivot.

lift forces on the pinwheel's blades.

Suppose you are a teacher, and, to your excitement, the local weather person comes for a classroom visit! She is talking about tornadoes and says that there is air moving very rapidly upwards through the funnel but air standing basically still outside the funnel. Such motion would cause A. houses on the ground to implode. B. the funnel pressure to be equal to the pressure outside. C. high pressure inside the funnel. D. low pressure inside the funnel.

low pressure inside the funnel.

If a golf ball were smooth rather than dimpled, it would A. travel much too far after being hit by a golf club. B. curve toward the left after being hit by the club of a right-handed golfer. C. curve toward the right after being hit by the club of a right-handed golfer. D. not travel as far after being hit by a golf club.

not travel as far after being hit by a golf club.

Imagine sitting on a merry-go-round and riding along as it spins. Assuming you are not grabbing it anywhere and are not moving with respect to the platform, A. static friction (directed inwards) causes you to accelerate. B. you are not accelerating because you aren't moving on the platform. C. static friction (directed outwards) causes you to accelerate. D. sliding friction makes you accelerate inwards.

static friction (directed inwards) causes you to accelerate.

The Coelocanth is a very interesting, quite primitive fish that live deep in the ocean. Watching these beautiful creatures on a nature documentary, you notice that they are able to stay basically at one position in the water with only slight movements of its lobed fins. This indicates that A. the density of the fish is less than the density of the water. B. you don't have to be athletic to get on a documentary. C. the density of the fish is greater than the density of the water. D. the density of the fish is about equal to the density of the water.

the density of the fish is about equal to the density of the water.

You are filling a jar of honey from the spigot at the bottom of a large barrel at the grocery store. The honey flows extremely slowly, so the store manager has the barrel refilled. Now the honey flows much more rapidly from the spigot because A. the pressure of the honey at the bottom of the barrel increases as the height of honey in the barrel increases. B. the viscosity of the honey decreases as the height of honey in the barrel increases. C. the viscosity of the honey increases as the height of honey in the barrel increases. D. the density of the honey decreases as the height of the honey in the barrel increases.

the pressure of the honey at the bottom of the barrel increases as the height of honey in the barrel increases.

Suppose you have an aquarium and you notice that you have a solid plastic decoration and a rock of about the same volume but twice as dense, and both are totally submerged in the water. The buoyant force on the plastic object is about ___________as that on the rock. A. half as big B. one quarter as big C. the same D. twice as big

the same

When you pour honey into a bowl, it flows smoothly. If you did the same with water, it would splash. These different behaviors occur because honey's high A. momentum keeps it moving in a straight line while water's low momentum allows it to turn abruptly in many different directions. B. mass keeps it flowing smoothly while water's low mass allows it to acquire lots of angular momentum. C. density keeps it flowing smoothly while water's low density allows it to float upward and splash about. D. viscosity keeps it flowing smoothly while water's low viscosity allows inertia to break its flow into many separate pieces.

viscosity keeps it flowing smoothly while water's low viscosity allows inertia to break its flow into many separate pieces.