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

A body is held immersed in a liquid. (i) Name the two forces acting on the body and draw a diagram to show these forces. (ii) State how the magnitudes of two forces mentioned in part (i) determine whether the body will float or sink in liquid when it is released. (iii) What is the net force on the body if it (a) sinks and (b) floats? 

When a piece of wood is suspended from the hook of a spring balance, it reads 70 gf. The wood is now lowered into water. What reading do you expect on the scale of spring balance?

A solid iron ball of mass 500 g is dropped in mercury contained in a beaker. (a) Will the ball float or sink? Give reasons. (b) What will be the apparent weight of the ball? 

Draw a diagram to show the forces acting on a body floating in water with its some part submerged. Name the forces and show their points of application. How is the weight of water displaced by the floating body related to the weight of the body itself?

A block of wood is so loaded that it just floats in water at room temperature. What change will occur in the state of floatation, if

(a) Some salt is added to water, (b) Water is heated?

Give reasons. 

A body of volume V and density ρ_s , floats with volume v inside a liquid of density ρ_L. Show that `"v"/V = ρ_s/ρ_L` .

Why is the floating ice less submerged in brine than in water? 

An iron nail sinks in the water while an iron ship floats on water. Explain the reason. 

A piece of ice floating in a glass of water melts, but the level of water in the glass does not change.

Give reasons.

Hint: Ice contracts on melting. 

Explain the following : 

Icebergs floating in sea are dangerous for ships.

For a floating body, its weight W and upthrust F_B on it are related as :

A body of weight W is floating in a liquid. Its apparent weight will be

A body floats in a liquid A of density ρ₁ with a part of it submerged inside the liquid, while in liquid B of density ρ₂ it is totally submerged inside the liquid. The densities ρ₁ and ρ₂ are related as : 

A weather forecasting plastic balloon of volume 15 m³ contains hydrogen of density 0.09 kg m^-3. The volume of equipment carried by the balloon is negligible compared to its own volume. The mass of an empty balloon alone is 7.15 kg. The balloon is floating in air of density of 1.3 kg m^-3. Calculate:

(i) The mass of hydrogen in the balloon,
(ii) The mass of hydrogen and balloon,
(iii) The total mass of hydrogen, balloon and equipment if the mass of equipment is x kg,
(iv) The mass of air displaced by balloon and
(v) The mass of equipment using the law of floatation. 

Explain the following term :

Plane mirror 

Draw diagram/diagrams to show them. 

Write three characteristics of the image formed by a plane mirror?

What is meant by lateral inversion of an image in a plane mirror? Explain it with the help of a ray diagram. 

The image formed by a plane mirror is :