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:
(a) Soles of shoes and tyres of vehicles are grooved: To increase grip (friction) by creating interlocking structures. Prevents slippage and skidding.
(b) Lubricants applied between the moving part of a machine: To reduce heating and energy loss. Also reduces wear and tear by allowing easy movement/sliding by reducing friction.
(c) People often rub their hands in winter: Rubbing friction causes heat
(d) It is easier for the fish to swim in water: Fishes have streamlined bodies accompanied by fins and tail which helps it to swim and steer in water more effectively.
(e) Oil is applied in the hinges of doors: To reduce friction and creaking noises by allowing smooth travel of hinges on the axis. Reduces damage.
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Answer:
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Explanation:
a) to not slip due to friction .
b) to decrease the friction so that the machine parts don't damage and wear and tear..
c) to produce heat to keep themselves warm during the extreme cold weather.
d) due to their streamline body shape they can move faster and therefore produce very less friction.
e) so that the doors don't produce sound when open or closed. The oil decreases friction that helps the metal hinges move smoothly.