Q9. Give examples to show that friction is both a friend and a foe.
Friction acting as a friend:
(a) It aids us to walk and cars to move on the roads.
(b)Fire can be ignited using friction.
Friction acting as a foe:
(a) It causes the efficiency of engines to decrease and also damages machinery.
(b) Friction causes soles of shoes and tires to wear off.