Question

Which of the following methods cannot be used to increase friction?

• A. Polishing the surfaces
• B. Using dry surfaces
• C. Increasing weight of the body
• D. Using lubricants like oil and grease

Answer 1

Answer: (A), (D)

Using lubricants like oil and grease

By using lubricants like oil and grease, friction can be decreased. Hence option A, i.e. using lubricants like oil and grease, cannot be used to increase the friction.
The greater the weight of an object, greater is the friction between it and the surface in contact with it. So option B, i.e. increasing weight of the body will increase the friction and hence is not a correct option.
Polishing and making the surfaces smooth reduces the irregularities on the surface of an object and hence reduces the friction. So option C, polishing the surfaces, cannot be used to increase the friction.
Moisture or water can act like a lubricant between surfaces. Therefore wet surfaces, for example wet floors, have less friction and are slippery. Thus making surfaces dry will increase the friction and hence is not a correct option.