16. Give reasons
(i)
A few drops of oil are poured on the hinges of a door.
Compressed and purified air is considered a good lubricant.
(iii) We use ball bearings in shafts of motors.
Answers
Answer: i
Explanation:
The correct reasons are as follows:-
(i) A few drops of oil are poured on the hinges of a door.
To remove friction on the irregularities so that the door moves smoothly. Oil is a lubricant. So the interconnected irregularities are dissolved.
(ii) Compressed and purified air is considered a good lubricant.
The flow of compressed and purified air lower the friction in machines and systems, therefore it acts as a good lubricant.
(iii) We use ball bearings in shafts of motors.
Ball-bearing is a type of rolling-element bearing that carries loads, reduces friction and positions moving machine parts. It uses balls to separate two bearing rings, to reduce surface contact and friction across moving planes. Due to this it is used in shafts of motors.