13. A girl stands on a box having 60 cm length, 40 cm breadth and 20 cm width in three ways. In which of the following cases, pressure exerted by the brick will be :(a) Maximum when length and breadth form the base(b) Maximum when breadth and width form the base(c) Maximum when width and length form the base(d) The same in all the above three cases

a car travels half distance with the speed of 20m/s and next half distance travel with 30 m/s , the average speed of the car is

A hockey ball of mass 200g travelling from west to east at 10m//s is struck by a hockey stick. As a result, the ball gets turned back and now has a speed of 5m//s. If the ball and hockey stick were in contact for 0.2s, Calculate (i) initial and final momentum of the ball (ii) rate of change of momentum of the balll (iii) force exerted by hockey stick on the ball.

Which step is not involved in the carbon-cycle ?

Draw a neat labelled diagram of a vernier callipers.

Why are lead compounds are added to petrol? How is it harmful?