A cheetah, on seeing a prey, moves towards him at a very high speed. What causes the movement of his muscles ? How does the chemistry of cellular components of muscle change during this event ?

A person moves with a velocity v towards a plane mirror. With what velocity does his image move towards him ?

A man from the top of a 100 m high tower sees a car moving towards the tower at an angle of depression 30°. After some time, the angle of depression becomes 60°. What is the distance travelled by the car during this time ?

When extremely small particles X derived from the anther of a flower were suspended in a liquid Y and observed through a microscope, it was found that the particles X were moving throughout the liquid Y in a very zig-zag way. It was also observed that warmer the liquid Y, faster the particles X moved on its surface. What could particles X be ? (b) What do you think liquid Y is ? (c ) What is zig-zag movement of X known as ? (d) What is causing the zig-zag movement of particles X ? (e) Name the scientist who discovered this phenomenon. (f) What does this experiment tell us about the nature of liquid Y ?

When a beam of sunlight enters a room through a window, we can see tiny particles X suspended in a gas (or rather a mixture of gases) Y which are moving rapidly in a very haphazard manner. (a) What could particles X be ? Name the gas (or mixture of gases) Y. (c ) What is the phenomenon exhibited by particles X known as ? (d) What is causing the movement of particles X ? (e) What conclusion does the existence of this phenomenon give us about the nature of matter ?

An athlletic coach told his team that muscle times speed equals power. What dimesions does he view for muscle?

(a) When a molecule (or an elastic ball) hits a (massive) wall, it rebounds with the same speed. When a ball hits a massive bat held firmly, the same thing happens However, when the bat is moving towards the ball, the ball rebounds with a different speed. Does the ball move faster or slower? (b) When gas in a cylinder is compressed by pushing in a piston. Its temperature rises. Guess at an explanation of this in terms of kinetic theory using (a) above (c) What happens when a compressed gas pushes a piston out and expands. What would you observe? (d) Sachin Tendulkar uses a heavy cricket bat while playing. Does it help him in any way?