Question

22. Give reason.
a) An athlete is advised to come to stop slowly after finishing a fast race.
b) Carts with rubber tyres are easier to ply than those with iron tyres.
c) Blades of an electric fan continue to rotate for some time after the current is switched off.​

Answer 1

a. it is done to decrease the rate of change of momentum by increasing the time interval and hence ,reducing the impact force

b.Carts with rubber tyres are easier to ply than those with iron wheels, this is because coefficient of friction between rubber tyres and road is much smaller than the coefficient of friction between the iron wheel and the road

c.The electric fan continues to rotate for some time after the current is switched off due to rotational inertia force.

Answer 2

a) It is done to decrease the rate of change of momentum by increasing the time interval and hence ,reducing the impact force. This will reduce or avoid any injury.

b) Carts with rubber tyres are easier to ply than those with iron wheels, this is because coefficient of friction between rubber tyres and road is much smaller than the coefficient of friction between the iron wheel and the road.

c) The blades of an electric fan continue to rotate for some time because of inertia of motion. The blades of the fan were in motion. Hence, they will take time to come to rest after being switched off.