(English Medium) ICSE Class 9 - CISCE Question Bank Solutions for Physics

The density of water is : 

Calculate the mass of air in a room of dimensions 4.5 m × 3.5 m × 2.5 m if the density of air at N.T.P. is 1.3 kgm^-3 . 

A piece of iron weighs 44.5 gf in air. If the density of iron is 8.9 × 10³, find the weight of iron piece when immersed in water.

A jeweller claims that he makes ornaments of pure gold that has a relative density of 19.3. He sells a bangle weighing 25.25 gf to a person. The clever customer weighs the bangle when immersed in water and finds that it weighs 23.075 gf in water. With the help of suitable calculations, find out whether the ornament is made of pure gold or not.

[Hint : calculate R.D. of material of bangle which comes out to be 11.6].

How does the density ρ_s of a substance determine whether a solid piece of that substance will float or sink in a given liquid ρ_L? 

Explain why an iron nail floats on mercury, but it sinks in water.

Hint : Density of iron is less than that of mercury, but more than that of water. 

A body floats in a liquid with a part of it submerged inside the liquid. Is the weight of floating body greater than, equal to or less than the upthrust?

A man first swims in sea water and then in river water. (i) Compare the weights of sea water and river water displaced by him.

(ii) Where does he find it easier to swim and why? 

What can you say about the average density of a ship floating on water in relation to the density of water? 

A loaded cargo ship sails from sea water to river water. State and Explain your observations. 

Explain the following : 

An egg sinks in fresh water, but floats in a strong salt solution.

Explain the following : 

Toy balloons filled with hydrogen rise to the ceiling, but if they are filled with carbon dioxide, then they sink to the floor.

Explain the following : 

As a ship in harbour is being unloaded, it slowly rises higher in water.

Explain the following : 

A balloon filled with hydrogen rises to a certain height and then stops rising further.

Explain the following : 

A ship submerges more as it sails from sea water to river water.

A rubber ball floats on water with its 1/3^rd volume outside water. What is the density of rubber? 

A block of wood of mass 24 kg floats on water. The volume of wood is 0.032 m³. Find: 

1. the volume of block below the surface of water,
2. the density of wood.

(Density of water = 1000 kg m⁻³)

A wooden cube of side 10 cm has mass 700 g. What part of it remains above the water surface while floating vertically on water surface? 

A piece of wax floats on brine. What fraction of its volume is immersed?