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 student places a candle flame at a distance of about 60 cm from a convex lens of focal length 10 cm and focuses the umage of the flame on a screen. After that he gradually moves the flame towards the lens and each time focuses the image on the screen. (a) In which direction-toward or away from the lens, does he move the screen to focus the image ? (b) How does the size of the image change ? (c) How does the intensity of the image change as the flame moves towards the lens ? (d) Approximately for what distance between the flame and the lens, the image formed on the screen is inverted and of the same size ?

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

A uniform string of length 'L' is suspended from a point on the ceiling. A small wave pulse is now introduced at its lowest end and it starts moving up towards the ceiling. (i) What will be the speed of the wave pulse when it has moved up a distance x? (ii) How much time does this wave pulse take to reach the ceiling?