PHYS 1030 Ch 9

Archimedes Principle states that

an object immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid.

Why does a hairspray can explode if placed in a fire?

both a and b

It is observed that as bubbles rise in a deep column of water, the diameter of the bubbles increases as the pressure on the bubble decreases. This is best explained by

Boyle's Law

In the constriction mentioned in the previous problem the fluid pressure will

decrease

When a fluid passes through a constriction in a pipe or hose the velocity of the fluid will

increase

The volume of a gas is _____ to pressure if the temperature remains the same.

inversely proportional

Pascal's Principle

pressure applied to a fluid is transmitted throughout the fluid

The volume of a gas is _____ to temperature if the pressure remains the same.

proportional

A balloon inflated with helium is able to float toward the ceiling because

the balloon and the gas it contains weigh less than the air displaced by the balloon.

Three individuals stand with all of their weight on the heel of one foot: a man of weight 600 N and a heel area of 100 cm2, a child of weight 200 N and a heel area of 25 cm2 and woman of weight 450 N and a heel area of 2 cm2. The one exerting the least pressure on the ground is:

the man.

The area of a blood vessel shrinks in size to half of its original area due to clotting. By what factor will the blood velocity rate change if you ignore friction?

twice as fast

Two cylindrical pipes both carry an ideal fluid (zero viscosity) in laminar flow. Pipe A has radius RA = 2 cm and flow velocity vA = 8 cm/s. Pipe B has radius RB = 4 cm and flow velocity vB = 4 cm/s. Compared to the rate of flow in pipe A, that in pipe B is

twice as large.

The volume of air in a balloon is 4.5 liters when inflated. When it cools the volume shrinks to 1.1 liters. If the original temperature 21.0 C, what new temperature would be required to produce that change if everything else is constant?

-201 degrees C

How does the velocity of water moving through a narrow pipe, that is connected to a wider pipe, compare to the velocity of water moving through the wider pipe? (velocity not flow rate)

The velocity in the small pipe is greater.

A child is drinking a liquid with a straw. Which of the following statements is true

When the pressure in the straw is reduced, atmospheric pressure on the surface of the liquid pushes the liquid up the straw.

Do glass windows in aluminum frames have expansion joints? Explain.

Yes, some are soft rubber and you can see them. Some just use an air space to allow for expansion.

A steel rod is 2.55 cm long at 16 o C in an operating room. It is placed in a patient's leg where it rises to 37 o C. What will the change in length be?

0.000643 cm

The input piston of a hydraulic jack is 1.20 cm in diameter. The output piston is 12.2 cm in diameter. The input force is 141 newtons. What is the input pressure in pascals?

1,246,684

250 newtons of pressure are placed on a rectangle 1 cm wide by 2 cm long. What is the pressure in pascals?

1,250,000 Pa

The input piston of a hydraulic jack is 1.20 cm in diameter. The output piston is 12.2 cm in diameter. The input force is 111 newtons. What is the output force in newtons?

11473

A hydraulic device is used to lift the bucket of a backhoe. The input is a round cylinder that is 1.0 cm in radius. The output piston is round and 6.0 cm in radius. How much can it lift if the input force is 500 newtons?

18,000 N

A hydraulic device is used to lift the bucket of a backhoe. The input is a round cylinder that is 2.0 cm in diameter. The output piston is round and 12.0 cm in diameter. How much can it lift if the input force is 500 newtons?

18,000 N

You put 25 pounds of force on the input piston of a hydraulic jack. The piston is has an area of 2.4 cm2 while the output piston is 18 cm2. How much weight will the jack lift? You may use the units pounds.

188 pounds

A gas originally occupies a volume of 0.5 m3 at a pressure of 100 kPa. It is slowly allowed to expand until the volume is 2.5 m3. Assuming the temperature is kept constant, the final pressure will be:

20 kPa.

A hydraulic jack has an input piston that is 1.2 cm2 in area and an output piston that is 144 cm2 in area. How much input or effort force in newtons is needed to lift a car that weighs 24,000 newtons?

200

A boat floating in a large pool and displaces 25 liters of water. What is the buoyant force on the boat. 1000 liters = 1 m3 Density of water = 1000 kg/m3

245 newtons

A block of aluminum has dimensions of 20 cm x 20 cm x 40 cm and weighs 423 N in air. What will it appear to weigh when below the surface of a fresh water lake? (Recall that freshwater has a density of 1000 kg/m3.)

266 N

There are 40 ml of air in a large syringe. With the exit hole plugged, you squeeze the air down to about 10 ml. If the original pressure was 1.0 atmosphere, how much pressure do you need to exert to squeeze it down to 10 ml in atmospheres?

4 atm

One section of a pipe carrying water has a cross-sectional area of 20 cm2; in this section the water has flow velocity of 1.0 m/s. Another section of this pipe has a constricted cross-sectional area of 5 cm2. If the flow is steady, what is the water velocity in the cons tricted section?

4.0 m/s

The volume of air in a balloon is 4.5 liters when inflated. External pressure decreases the volume to 1.1 liters. If the original pressure was 1.00 atmosphere, what pressure would be required to produce that change if everything else is constant?

4.1 atm

40 ml of air is in a large syringe. If you plug the hole, you can squeeze the air down to about 10 ml. If the original pressure was 1.0 atmosphere, how much pressure do you need to exert to squeeze it down to 10 ml in Pascals?

405,000 Pa

A fireman's water hose has a diameter of about 4.0 inches. The water is flowing through it at about 19.0 m/s. The nozzle's diameter drops to about 0.80 inches. If there is no friction, what would the exit velocity of the water be?

475

A water hose is 1.0 inch in diameter. A squirt tip only 0.25 inches in diameter is attached to the end. If the water is fed into the hose at 3.0 meters/sec, how fast will it come out the squirt tip?

48 m/s

If the atmospheric pressure is 15 lb/in2 , what is the corresponding downward force on the top of a horizontal square area 6 inches on each side?

540 lbs

A hydraulic jack is used to lift a load of weight 1000 N. The load-bearing cylinder has a radius of 4 cm, and the other piston has a radius of 1 cm. What force must be exerted on the smaller piston to support the load?

62.5 N

How does the flow rate of water moving through a narrow diameter pipe, that is connected to a larger pipe, compare to the flow rate of water moving through the larger diameter pipe? Flow rate refers to liters/minute, etc. Ignore friction.

The flow rates are the same.

Which law or principle says that the buoyant force exerted on an object placed in a fluid equals the weight of the displaced fluid?

Archimedes' Principle

pressure

Force per unit area.

Which is NOT one of 2 ways you can increase the pressure inside a fixed volume container?

Decrease the temperature

When you push down slowly on a syringe, the fluid shoots out of the needle with a high speed. Which equation explains why this happens?

Equation of Continuity Av before=Av after

What is the difference between lift and buoyant force?

Lift occurs due to a difference in pressure on top and bottom of a surface, while buoyant force is a lifting force caused by the displacement of the fluid the object is in.

The fact that an incresed pressure on an enclosed fluid is transmitted uniformly through the volume of the fluid is known as(__________) law or principle.

Pascal's

What is the name of the law or principle that governs hydraulic systems and which states that an external pressure applied to a fluid is transmitted undiminished in all directions?

Pascal's Law

Which of the answers below is most correct?

Pressure has a capital P symbol, and the units are pascals, which has a Pa symbol

A woman changes from a high heel shoe with a 1 square centimeter heel to flats with a 4 square cm heel. Which statement is correct?

The force remains the same, but the pressure goes down.

What is meant by gauge pressure?

The gauge pressure is the total pressure inside of a container minus the pressure outside a container.