How many types of elements together make up the xylem tissue? Name them.

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.

Name the following.

(a) Tissue that forms the inner lining of our mouth.
(b) Tissue that connects muscle to bone in humans.
(c) Tissue that transports food in plants.
(d) Tissue that stores fat in our body.
(e) Connective tissue with a fluid matrix.
(f) Tissue present in the brain.

What are the functions of areolar tissue?

A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625 m.

What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?

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

How does the water kept in an earthen pot (matka) become cool during summer?

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.

Identify the solutions among the following mixtures.

(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.

A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m s^-2, with what velocity will it strike the ground? After what time will it strike the ground?

Explain how bats use ultrasound to catch a prey.