Buoyancy

Q.

A hollow spherical shell at outer radius $R$ floats just submerged under the water surface. The inner radius of the shell is $r$. If the specific gravity of the shell material is $\frac{27}{8}$ w.r.t water, the value of $r$ is:

1. $4/9R$

2. $8/9R$

3. $1/3R$

4. $2/3R$

Q.

What is a simple pendulum?

Q.

A block of wood floats on water with 1/4 th of its volume above the water surface. The density of the wooden block will be?

Take, density of water = 1 $gc{m}^{-3}$.

1. 0.25 $gc{m}^{-3}$

2. 0.50 $gc{m}^{-3}$

3. 0.75 $gc{m}^{-3}$

4. 1 $gc{m}^{-3}$

Q.

What is the principle of buoyancy ?

Q.

A body of volume V and density ρ is completely immersed in a liquid of density ρ_L . If g is the acceleration due to gravity, which of the following expressions are correct :

1) weight of the body = Vρg

2) upthrust on the body = VρLg

3) apparent weight of the body in liquid = VρLg

4) the loss in weight of the body = V(ρ-ρL)g

1. only 2 and 3

2. only 4

3. both 1 and 2

4. only 1

Q.

What is meant by the term buoyancy ?

Q.

Why do we feel lighter while swimming in a pool of water?

Q.

Define ‘buoyant force’. What is the cause of buoyant force? Explain an activity to show how buoyant force changes as the volume of an object immersed in water changes.

Q.

What do you mean by buoyancy? [1 MARK]

Q.

A pin or a needle floats on the surface of water, the reason for this is

1. Surface tension

2. Less weight

3. Upthrust of liquid

4. None of the above

Q.

Why do we feel lighter when we swim?

Q. A cube of density $800kg{m}^{-3}$ is floating in water. Volume of the cube is $2m^3$. Calculate the force of buoyancy acting on the body.
Density of water: ${\rho }_{water}=1000kg{m}^{-3}$

1. $1600N$
2. $16000N$
3. $8000N$
4. $10000N$

Q.

What will happen to the ship loaded in sea water to maximum capacity is moved to river water?

Q.

Why does the block of plastic released under the water come up to the surface of water

Q.

If the density of iron is $7.85gc{m}^{-3}$and the density of water is $1000kg{m}^{-3}$. then the relative density of iron is_____________.

Q.

The centre of gravity of a rectangle will be at its:

1. The intersection of its diagonal

2. Centre

3. Corners

4. At its periphery

Q. How to calculate tension in a string

Q.

An object of weight 500 N is floating in a liquid. The magnitude of buoyant force acting on it is

Q. What factors does buoyant force depend on?

1. Density of the fluid
2. Value of acceleration due to gravity at that place
3. Density of the object
4. Speed of the flowing water

Q. Motion of a motorcyclist is shown in the figure. Which of the following shows the distance-time graph for this motion?

1. 
2. 
3. 
4. 

Q.

The force applied on any surface in a direction perpendicular to it is called

1. pressure

2. force

3. buoyancy

4. thrust

Q. When you fill a bucket with full of water and introduce an empty mug get inverted we feel that some force and does not allow the mug 2 sink y

Q. Why liquids exert an upward buoyant force?

Q.

A solid body of weight 9.0 N is suspended by a string in the water. The tension in the string is 7.5 N. Find

1. the loss of weight of the solid in water,
2. the buoyant force exerted by water on the solid,
3. the volume of the body
4. the tension in the string if only half the volume of the body is immersed in water. Take the density of water as 1.0 x 10³ kg m^-3

Q. The density of tap water is less than that of sea water. if an object is immersed completely in both one by one, what will be the loss in weight?

Q. What are the factors on which pressure depends

Q.

A bucket filled with water feels heavier when it emerges above the surface of water.

1. True
2. False

Q.

The property of a fluid to exert an upward force on a body immersed partly or completely in it is called ________.

Q.

What do you understand by the term upthrust?

Q.

Name a liquid in which a solid iron ball can float.