Chapter 6 Tissues

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?

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?

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

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?

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?

A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.

How are pteridophytes different from the phanerogams?

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

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

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

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

If Z = 3, what would be the valency of the element? Also, name the element.

If bromine atom is available in the form of, say, two isotopes ⁷⁹₃₅ Br (49.7%) and ⁸¹₃₅ Br (50.3%), calculate the average atomic mass of bromine atom.

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.

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?

During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is, 3 × 10⁸ m s^-1.