Buoyancy and Floatation topics include: Buoyancy, metacenter and metacentric height, manometer and equilibrium conditions of submerged bodies. Buoyancy is the upward force exerted on an object submerged in a fluid. Floatation is the ability of an object to remain on the surface of a liquid or gas.  According to the principle of floatation, an object will float in a liquid if the buoyant force acting on it is equal to the object's weight. The volume of fluid displaced must also equal the volume of the object immersed in the fluid. If the object's weight exceeds the upthrust, it will... Show more

Buoyancy and Floatation topics include: Buoyancy, metacenter and metacentric height, manometer and equilibrium conditions of submerged bodies.

Buoyancy is the upward force exerted on an object submerged in a fluid. Floatation is the ability of an object to remain on the surface of a liquid or gas. 

According to the principle of floatation, an object will float in a liquid if the buoyant force acting on it is equal to the object's weight. The volume of fluid displaced must also equal the volume of the object immersed in the fluid. If the object's weight exceeds the upthrust, it will sink. 
Buoyancy is important in swimming because it helps the swimmer to stay closer to the surface. This is because the pressure experienced by the swimmer under the water is more than the pressure experienced above. 

Here are some examples of buoyancy and floatation:
Lump of clay: If you drop a lump of clay in water, it will sink. However, if you mold the same lump of clay into the shape of a boat, it will float. Because of its shape, the clay boat displaces more water than the lump and experiences a greater buoyant force.
Swimmers: Buoyancy helps swimmers to stay closer to the surface.

Show less

Fluid Mechanics Practice Test: Buoyancy and Floatation

Time left 00:00

25 Questions

1. A uniform body of size 4 m long * 2.5 m wide * 1.5 m deep floats in water. What is the weight of the body if depth of immersion is 1 m ?

294.3 kN147.1 kN588.6 kN73.5 kN

2. A student wants to find the absolute pressure of water at a point below the surface of water. He has a barometer and a manometer pressure gauge. The barometer reads 1.3152 bar where as the manometer pressure gauge reads 0.3152 bar. What is the absolute pressure? (Assume that pressure at one end of the manometer is atmospheric.)

0.3152 bar1 bar1.3152 bar1.6304 bar

3. A manometric liquid should suitably have _________

Low density & High Vapour pressureHigh density & Low Vapour pressureHigh density & High Vapour pressureLow density & Low Vapour pressure

4. If the magnitude of dimension of a rectangular wooden block is length>breadth>height, then for it to float on the water, it should be immersed in what manner?

It should be immersed such that height is partially immersedNone of the mentionedIt should be immersed vertically such that length is partially immersedIt should be immersed horizontally such that breadth is partially immersed

5. A block of material of specific gravity 0.45 floats in water. Determine the meta-centric height of the block if its size is 3 m * 2 m* 0.8 m.

0.506 m0.127 m0.376 m1.012 m

6. A solid cylinder of 15 cm diameter and 40 cm long, consists of two parts made of different materials. The first part at the base is 1.5 cm long and of specific gravity=6.5. The other part of the cylinder is made of the material having specific gravity 0.75. State, if the it can float vertically in water.

None of the mentionedIt will floatData insufficientIt will not float

7. A simple U-tube manometer can measure negative gauge pressures.

FalseTrueDon't KnowMaybe

8. Submarines use principle of ‘neutral buoyancy’ to go into the water.

Don't KnowFalseMaybeTrue

9. A body of dimensions 2.7 m * 3.8 m * 2.5 m, weighs 2500 N in water.Find its weight in air.

254.12 kN127.06 kN508.25 kN101.65 kN

10. A wooden cylinder of sp.gr. = 0.6 and circular in cross-section is required to float in oil(sp.gr. = 0.90). Find the L/D ratio for the cylinder to float with its longitudinal axis vertical in oil, where L is the height of cylinder and D is its diameter.

None of the mentionedL/D<3/4L/D<2/3L/D<9/16

11. The metacentric height is affected by the change in density.

Don't KnowTrueFalseMaybe

12. A rectangular pontoon is 5 m long, 3 m wide and 1.40 m high. The depth of immersion of the pontoon is 0.60 m in seawater. If the centre of gravity is 0.7 m above the bottom of the pontoon, determine the metacentric height. The density for seawater = 1045 kg/m³.

0.2710.0680.1350.543

13. How can relatively denser object be made to float on the less dense fluid?

By altering the forces acting on the objectBy altering the shape.By altering the shear forces acting on the objectNone of the mentioned

14. In unstable equilibrium what is the relation between forces?

None of the mentionedBuoyancy force < Weight of bodyBuoyancy force > Weight of bodyBuoyancy force= Weight of body

15. When body is completely or partially immersed in a fluid, how much its weight be distributed for it to be in stable equilibrium.

Is independent of weight distributionAround the upper partNone of the mentionedAround the lower part

16. In a U-tube mercury manometer, one end is exposed to the atmosphere and the other end is connected to a pressurized gas. The gauge pressure of the gas is found to be 40 kPa. Now, we change the manometric fluid to water. The height difference changes by: (ρmercury = 13600 kg/m³, ρwater = 1000 kg/m³).

Remains unchanged (0%)92.64 %13.6%1260%

17. In the manometer given above, 2 immiscible fluids mercury (ρ = 13600 kg/m³) and water (ρ = 1000 kg/m³) are used as manometric fluids. The water end is exposed to atmosphere (100 kPa) and the mercury end is exposed to a gas. At this position, the interface between the fluids is at the bottom most point of the manometer. Ignore the width of the manometer tube and the radius of curvature. The value of h is found to be 9.45 m. The height of the mercury column is given to be 75 cm. Find the gauge pressure of the gas. (g = 9.8 m/s²)

0 kPa200 kPa100 kPa50 kPa

18. Proper explanation for metacentre is:

Intersection of line passing through new centre of buoyancy and centre of gravity.point about which body starts oscillating when it is given small angular displacementAll of the mentionedPoint at which line of action of force meets the normal axis of body when it is given angular displacement

19. A stone weighs 450 N in air and 200 N in water. Compute the volume of stone.

.025 m3.05 m3.075 m3None of the mentioned

20. As a balloon rises in the air its volume increases, at the end it acquires a stable height and cannot rise any further.

Don't KnowMaybeTrueFalse

21. Meta centre always lies below the centre of gravity

Don't KnowTrueMaybeFalse

22. In stable equilibrium for completely submerged bodies what is the relation between forces?

Buoyancy force= Weight of body,the centre of buoyancy is below the centre of gravity.Buoyancy force < Weight of bodyNone of the mentionedBuoyancy force=Weight of body, the centre of buoyancy is above the centre of gravity.

23. Both ends of a U-tube manometer are exposed to the atmosphere. There exists a possibility that the height difference of the manometer is non-zero. True or False?

FalseMaybeDon't KnowTrue

24. Find the density of metallic body which floats at the interface of mercury of sp.gr 13.6 and water such that 40 % of its volume is sub-merged in mercury and 60% in water.

3020 kg/m324160 kg/m36040 kg/m312080 kg/m3

25. In a U-tube manometer, one end is open to the atmosphere, the other end attached to a pressurized gas of gauge pressure 40 kPa. The height of the fluid column in the atmospheric side is 60 cm, and that on the gas side is 30 cm. The manometic fluid used is: (Take g = 9.8 m/s²).

OilMercuryWaterLiquid ammonia