If action is always equal to the reaction, explain how a horse can pull a cart.

Convert into mole.

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

Why is the atmosphere essential for life?

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

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?

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?

In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
  •  if you get jaundice,
  •  if you get lice,
  •  if you get acne.

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?

Name the technique to separate

(i) butter from curd,
(ii) salt from sea-water,
(iii) camphor from salt.

List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?

What is the utility of tissues in multi-cellular organisms?

The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?

Why is it not possible to see an atom with naked eyes?

Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle.

Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall.

In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
  •  if you get jaundice,
  •  if you get lice,
  •  if you get acne.

Why?

Explain the following giving examples.

(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension

Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.

Where is apical meristem found?

A batsman hits a cricket ball which then rolls on a level ground. After covering a short distance, the ball comes to rest. The ball slows to a stop because

(a) the batsman did not hit the ball hard enough.
(b) velocity is proportional to the force exerted on the ball.
(c) there is a force on the ball opposing the motion.
(d) there is no unbalanced force on the ball, so the ball would want to come to rest.