Question 1

What causes friction between two surfaces in contact?

Accepted Answer

Friction is caused by the irregularities on the two surfaces in contact. Even surfaces that appear very smooth have a large number of minute irregularities on them. When two surfaces are pressed together, these irregularities interlock with one another, causing opposition to motion.

Question 2

Which type of friction comes into play when an object is just about to slide over a surface?

Accepted Answer

Static friction comes into play when an object is just about to move or slide over a surface, representing the maximum opposition offered before the actual movement begins.

Question 3

Why is it easier to slide a box that is already in motion than to start it moving from rest?

Accepted Answer

Sliding friction is slightly less than static friction because the interlocking of surface irregularities does not get enough time to properly lock when the object is already in motion.

Question 4

Which of the following types of friction is the least?

Accepted Answer

Rolling friction is the least among static, sliding, and rolling frictions because when one body rolls over another, the area of contact and interlocking is minimized.

Question 5

What is the specialized shape given to objects moving through fluids to reduce friction called?

Accepted Answer

A streamlined shape is given to objects like airplanes and ships moving through fluids (air or water) to reduce fluid friction or drag.

Friction — MP Board Class 8 Science Important Questions & Revision Notes