The teacher instructed three students A, B and C respectively to prepare a 50% (mass by volume) solution of sodium hydroxide (NaOH). A dissolved 50g of NaOH in 100 ml of water, B dissolved 50g of NaOH in 100g of water while C dissolved 50g of NaOH in water to make 100 ml of solution. Which one of them has made the desired solution?

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?