Friction - Class 8, Science - MCQ Test 3 - Class 8 MCQ

Frictional force is always between two surfaces in contact with each other.

Sliding friction is less than the friction that builds up before sliding, i.e., static friction. Hence, sliding friction is less than 7 N.

Glass has comparatively a better polished and regular surface and so, it has the least friction.

The use of ball bearings causes rolling friction which is much less than the sliding friction.

Friction is desirable to stop or reduce speed of a speeding vehicle. When the brakes are applied in a speeding vehicle, they rub against the wheels in motion. Due to the friction between the brakes and wheels, the speed of vehicle is reduced or it may come to stop.

Powder is a lubricant and reduces friction. Hence, for decreasing friction, carrom board is usually powdered before playing.

Rolling reduces friction. Rolling friction is the least amongst the three kinds of frictions, rolling, sliding and static friction.

The frictional force exerted by fluids is called drag.

A streamlined body reduces drag (friction) during motion.

For the given surfaces static friction is somewhat greater than sliding friction as well as-rolling friction. It is easier to roll than to slide. Hence, sliding friction is greater than rolling friction. The decreasing order of magnitude of friction is static, sliding and rolling.

Rolling friction is much less than sliding friction. So, rolling a drum is easier.

Due to the very high speed of meteor when it enters the earth's atmosphere, the heat produced by the friction of air is very large which causes the meteor to burn.

Due to increased friction, greater frictional heat is produced in the match stick which thus lights up easily.

Spikes in the shoes increase friction and prevent slipping.

When we push the ground with our feet, the friction provides a forward reaction to our push and makes us move forward. (Walking on slippery ground is difficult because the frictional force is not enough to prevent slipping).

Statement (A), (B) and (C) are correct.

Friction opposes the relative motion of objects. In its absence, a moving object will not stop.

The wearing out of the soles of shoes is a disadvantage of friction.

Leaves falling from a tree onto the ground is due to the effect of gravitational force and not due to frictional force.

Since, rolling friction is less than sliding friction, the tyres are made circular instead of flat.