Why does a sharp knife cut objects more effectively than a blunt knife?

Which force is responsible for raising our body hair when we try to take off a terylene or polyester shirt in the dry weather?

Name the type of forces involved in the following :

(a) A horse pulling a cart.

(b) A sticker attached to steel almirah without glue.

(c) A coin falling to the ground on slipping from hand.

(d) A plastic comb rubbed in dry hair picking up tiny pieces of paper.

(e) A moving boat coming to rest when rowing is stopped.

Explain why, wooden (or concrete) sleepers are kept below the railway line.

Explain why, a wide steel belt is provided over the wheels of an army tank.