Arrange the following speeds in increasing order (keeping the least speed first): (i) An athlete running with a speed of 10 m s . (ii) A bicycle moving with a speed of 200 m min . (iii) A scooter moving with a speed of 30 km h .

For an athlete, speed = 10 m s . ...(1) For a bicycle, speed = 200 m min = 200 60 m s = 3 . 33 m s . ...(2) For a scooter, speed = 30 km h = 30 × 1000 3600 m s = 8 . 33 m s . ...(3) Thus, from (1), (2), and (3), we get 200 m min < 30 km h < 10 m s . Thus, speed of a bicycle < speed of a scooter < speed of an athlete.

A train starting from Railway Station attains a speed of 21 m s in one minute. Find its acceleration.

The acceleration is given by, a = v - u t . Where, a = acceleration of the body , v = final velocity of the body , u = initial velocity of the body , t = time taken for change in velocity . For a train, it is given that, The initial velocity, u = 0 m s . The final velocity, v = 21 m s . The time taken, t = 60 s . Therefore, acceleration, a = v - u t ⇒ a = 21 - 0 60 ⇒ a = 0.35 m s 2 Thus, acceleration of a train, a = 0 .35 m s 2 .