Write an expression for the work done when a force is acting on an object in the direction of its displacement.

Convert into mole.

(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

Why is the atmosphere essential for life?

Why is the weight of an object on the moon 1/6th its weight on the earth?

What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?

Why are we normally advised to take bland and nourishing food when we are sick?

You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?

Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?

List any three human activities that you think would lead to air pollution.

Which tissue makes up the husk of coconut?

Complete the table:

What is the mass of:

(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?

What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?

Give three features of cardiac muscles.

How are simple tissues different from complex tissues in plants?

What are the constituents of phloem?

An electric heater is rated 1500 W. How much energy does it use in 10 hours?

A battery lights a bulb. Describe the energy changes involved in the process.

Give reason for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.