Class Work Fluids Problems

## SECTION 1

N/m2 = Pascal
atm = 1.013 x x105 Pa
Bar = 1 x105 Pa
Torr = 1 mm of Mercury in a barometer
760 mm of Mercury in barometer = 1 atm
water density = 1000 kg/m

1. Using a scale and a graduated cylinder, find the density of a “BB” in kg/m2?

2. If the atmospheric pressure is 1.013 x 105 Pa, how much force is holding piece of newspaper down to the floor?

3. Generally, water beds are not allowed in apartments on the any floor other than the ground level. A full size water bed is 137.16 x 190.50 x 35.00 cm. If the density of water is exactly 1000 kg/m3, then how much force is exerted on the floor by the bed?

4. A swimmer lays her hand flat on the bottom of the diving well at a local pool. The bottom of the well is 3.5 meters below the surface and the swimmer’s hand has an area of 0.0752 m2. At the bottom of the pressure at the bottom of the pool’s diving well is 1.372 x 105 Pa. What force is being exerted on her hand from the water's pressure?

5. What is the force on the bottom of the bottle in the bottle bottom breaking demonstration?

6. When you drink from a straw you create a partial vacuum in your mouth. This allows the atmosphere to push the fluid up the straw. If the cross sectional of the straw is 1.00 cm3 , and you accomplish a feat of super human proportions by creating a perfect vacuum, (P = 0 Pa), in the straw to drink some water, then how long can the straw be (vertically)?

7. Point “A” is 4.0 m below the surface and point “B” is horizontally located to “A.” What is the pressure at both points?

8 How deep do you need to go under water to double the atmospheric pressure of 1 atm? Water density is exactly 1000 kg/m3.

9 The opening on garden hose has a diameter of 2.54 cm. and water lands 0.500 m away from the opening when the hose is held horizontally 1.25 m above the ground. If your thumb is placed over the opening such that the effective diameter of the opening is reduced to 0.500 cm, then where will the water land on the ground now?

10 If 2 gallons are emptied out of a large container in 20 seconds from a hole with an area of 4 cm2. then what is the velocity of the water when it exits? How high above the hole is the surface?

11 A house with a retgangular roof (5.00 m by 7.00 m) experiences a wind 55 mph (26.4 m/s) wind. What is the lifting force caused by the wind?

12 Your body has a density of about 1050 kg/m3. what would happen if you were to fall in a pit of “quicksand” with a density of 1200 kg/m3?

13 A block 2 cm x 5 cm x 6 cm high with a mass of 51.0 g is placed in a fluid with a density of 1100 kg/m3. Will the wood sink of float? If it floats, where is the water level on the block. IF it sinks, what is its acceleration?

 Section 2
1. The circular top pf a can of soda has a radius of 0.0320 m. The pull-tab has an area of 3.80 x 10-4 m2. The absolute pressure of the carbon dioxide in the can is 1.40 x105 Pa. Find the force that this gas generates
1. on top of the can (including the pull-tab’s area) and
2. on the pull-tab itself.

2. High-heeled shoes can cause tremendous pressure to be applied to a floor. Suppose the radius of a heel is 6.00 x 10-3 m. At times during normal walking motion, nearly the entire body weight acts perpendicular to the surface of such a heel. Find the pressure that is applied to the floor under the heel because the weight of a 50.0 kg woman.

3. A cylinder is fitted with a piston, beneath which is a spring, as in the drawing. The cylinder is open at the top. There is no friction. The spring constant of the spring is 2900 N/m. The piston has negligible mass and a radius of 0.030 m. When the air beneath the piston is completely pumped out,

1. how much does the atmosphere’s pressure cause the piston to compress?
2. How much work does the atmosphere to in compressing the spring?

4. The Mariana trench is located in the Pacific Ocean and has a depth of approximately 11,000 m. The density of seawater is approximately 1025 kg/m3.

1. If a diving chamber were to explore such depths, what force would the water exert on the chamber’s observation window (radius = 0.10 m)?
2. For comparison, determine the weight of a jumbo jet whose mass is 1.2 x 105 kg.

5. A water tower has a vertical pipe that is filled with water. The pipe is open to the atmosphere at the top. The pipe is 22 m high. At the bottom of this pipe is a hole with a cork in it.

a). What is the pressure at this hole when the cork is in the hole?

b). What is the pressure when the cork is removed and the water is allowed to squirt onto the ground?

6. A buoyant force of 26 N acts on a piece of quartz that is completely immersed in ethyl alcohol. What is the volume of the quartz? ?ethanol = 785.06 kg/m3

7. Oil is flowing with a speed of 1.22 m/s through a pipeline with a radius of 0.305 m. How many gallons of oil (1 gal = 3.79x10-3 m3) flow in a day?

8. A small crack forms at the bottom of a 15.0 m high dam. The effective crack area through which the water leaves is 1.00 x 10-3 m2.

a). What is the speed of the water flowing through this crack?

b). How many cubic meters of water per second flow through the crack?

9. An airplane wing is designed so that the speed of the air across the top of the wing is 248 m/s when the speed below the wing is 225 m/s. The density of air is 1.29 kg/m3. What is the lifting force on a wing that is rectangular and 2 m x 10 m?

10. Water is running out of a faucet, falling straight down, with an initial speed of 0.50 m/s. At what distance below the faucet is the radius of the stream reduced to half of its original radius at the faucet?

From class slideshows

by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)