Question

Friction in parts of a machine can be reduced by using_____.

• A. iron filings
• B. lubricants
• C. ball bearings
• D. both (b) and (c)

Answer 1

The correct option is D

both (b) and (c)

The explanation for the correct option

Step 1: Friction

1. When two surfaces are in contact with each other and the surface moves on the other surface, a force that acts in the opposite direction of motion of the object is called friction.
2. Friction is a contact force.

Step 2: Explanation for the correct answer

1. When the different parts of a machine come in contact with each other frictional force acts between the parts of the machine.
2. Due to this friction irritating sounds may be produced in the machine. So the friction should be reduced.
3. By using lubricants like oil, grease, and ball bearing in different parts of the machine friction can be reduced.

Hence, the correct answer is (D).