Tag: upthrust in fluids, archimedes' principle and floatation

Questions Related to upthrust in fluids, archimedes' principle and floatation

A ball weighing  $4 kg$  of density  $4000{ kg }\quad { m }^{ { -3 } }$  is completely immersed in water of density  $1000{ kg }\quad { m }^{ { -3 } }.$  Find the force of buoyancy on it. (Given $g = 10 { ms } ^ { - 2 }$)

  1. $100{ N }$

  2. $1{ N }$

  3. $20{ N }$

  4. $10{ N }$


Correct Option: D

A ship of mass $ 3 \times10$ initially at rest is pulled by a force of $5\times 10$ N  through a distance of  Assuming that the resistance due to water is negligible, the speed of the ship is 

  1. 1.5 m/s

  2. 68 m/s

  3. 0.1 m/s

  4. 5 m/s


Correct Option: C

A balloon has volume of $1500\, m^3$. It is filled with hydrogen $(\rho = 0.09\, gL^{-1})$. If the density of air is $1.29\, gL^{-1}$, it can lift a total weight of 

  1. $2400\, kg$

  2. $1600\, kg$

  3. $2700\, kg$

  4. $1800\, kg$


Correct Option: C

An object measuring $2\times 2\times 5{cm}^{3}$ has a mass of $16g$. It is put in water of density $1g/cc$. Percentage of its volume outside water while floating is

  1. $10$%

  2. $20$%

  3. $30$%

  4. $40$%


Correct Option: C

lce pieces are floating in a beaker  $A$  containing water and also in a beaker  $B$  containing miscible liquid of specific gravity  $1.2 .$  When ice melts, the level of

  1. Water increases in $A$

  2. Water decreases in $A$

  3. Liquid in $B$ decreases

  4. Liquid in $B$ increases


Correct Option: C

Statement I:- An ice ball is floating in water. Some stone pieces are embedded inside the ice. When ice will melt level of water will fall.
Statement I:- In floating condition,stone pieces will displace more liquid compared to the condition when they sink.

  1. Statement I is true,statement II is true and statement II is a correct explanation for statement I.

  2. Statement I is true,statement II is true and statement II is NOT the correct explanation for statement I.

  3. Statement I is true,Statement II is false.

  4. Statement I is false,Statement II is true.


Correct Option: A

A block of wood is floating in water in a closed vessel as shown in the figure. The vessel is connected to an air pump. When more air is pushed into the vessel, the block of wood floats with : (neglect compressibility of water)

  1. Larger part in the water

  2. Smaller part in the water

  3. Same part in the water

  4. At some instant it will sink


Correct Option: C

A block of wood floats is water with $ 2/5^{th} $ of its volume above the surface Calculate the density of wood.

  1. $ 0.6 g/cm^3 $

  2. $ 1.6 g/cm^3 $

  3. $ 2.5 g/cm^3 $

  4. $ 3.6 g / cm^3 $


Correct Option: C

A block of wood floats in a liquid with four-fifths of its volume submerged. If the relative density of wood is $0.8$, what is the density of the liquid in units of $kg\, m^{-3}$?

  1. $750$

  2. $1000$

  3. $1250$

  4. $1500$


Correct Option: C

We have two different liquids A and B whose relative densities are 0.75 and 1.0, respectively. If we dip solid objects P and Q having relative densities 0.6 and 0.9 in these liquids, then:

  1. P floats in A and Q sinks in B

  2. P sinks in A and Q floats in B

  3. P floats in B and Q sinks in A

  4. P sinks in B and Q floats in A


Correct Option: C
Explanation:

If solid object has higher density than liquid then it will sink in that liquid otherwise it will float.
R.D. of liquid A = 0.75
R.D. of liquid B = 1.0
R.D. of object P = 0.6
R.D. of object Q = 0.9

  • P has R.D. less then both the liquids. so it will float in both the liquids.
  • Q has R.D. more than liquid A, so it will sink in A.
  • Q has R.D. less than liquid B, so it will float in B.