7. Give reason for the following:
(a) Soles of shoes and tyres of vehicles are grooved.
(b) Lubricants applied between the moving part of a machine. (c) People often rub their hands in winter.
(d) It is easier for the fish to swim in water.
(e) Oil is applied in the hinges of doors.
Answers
Answer:
in order to provide friction cause rough surfaces have more friction
lubricants are applied on moving parts in order to reduce wear and tear caused by friction
people rub their hands in winter to get heat as rubbing produces heat
fishes have a streamlined body that's why they find it easy to swim in water
Answer:
(a) The soles of the shoes have grooves in order to increase friction between the surface of the floor and the soles of the shoes. This prevents slipping on the floor.
(b) The moving part of machine has always the problem of damaging because of the friction.So in these parts oil is usually applied to lessen the friction.So the machine will work properly.
(c) When we rub hands friction is produced between our hands which in turns produces heat. This causes us to feel warm.
(d) Fish swim by flexing their bodies and tail back and forth. Fish stretch or expand their muscles on one side of their body, while relaxing the muscles on the other side. This motion moves them forward through the water.
(e) Oil is a lubricant. it helps to reduce friction by being applied over the irregularities of a surface. So, there is no interlocking of irregularities, so, friction reduces, and the door moves smoothly.