What type of a force is friction?
Frictional force is always between two surfaces in contact with each other.
What is the value of sliding friction for an object which requires 7 N of force to move it from rest?
Sliding friction is less than the friction that builds up before sliding, i.e., static friction. Hence, sliding friction is less than 7 N.
Which of the following materials is likely to have the least friction?
Glass has comparatively a better polished and regular surface and so, it has the least friction.
Which of the following reduces friction in a rotating machine?
The use of ball bearings causes rolling friction which is much less than the sliding friction.
In which of the following cases is friction desirable?
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.
Why is a carrom board usually powdered before playing?
Powder is a lubricant and reduces friction. Hence, for decreasing friction, carrom board is usually powdered before playing.
Which of the following statements is correct?
Rolling reduces friction. Rolling friction is the least amongst the three kinds of frictions, rolling, sliding and static friction.
What is the frictional force exerted by fluids called?
The frictional force exerted by fluids is called drag.
Why are certain bodies streamlined?
A streamlined body reduces drag (friction) during motion.
In the decreasing order of magnitude, which of the following is correct?
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.
Which of the following activities is easier to perform on a drum of 10 kg?
Rolling friction is much less than sliding friction. So, rolling a drum is easier.
Why does a meteor burn upon entering the earth's atmosphere?
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.
Why are the head of a match stick and the sides of a match box deliberately made rough?
Due to increased friction, greater frictional heat is produced in the match stick which thus lights up easily.
Why are spikes provided in the shoes of athletes?
Spikes in the shoes increase friction and prevent slipping.
Which force prevents us from slipping while walking on the road?
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).
Which of the following statements is NOT true?
Statement (A), (B) and (C) are correct.
What will happen to a moving object if there is no friction?
Friction opposes the relative motion of objects. In its absence, a moving object will not stop.
Which of the following is a disadvantage of friction?
The wearing out of the soles of shoes is a disadvantage of friction.
Which of the following is NOT an effect of frictional force?
Leaves falling from a tree onto the ground is due to the effect of gravitational force and not due to frictional force.
Why are tyres made circular in shape?
Since, rolling friction is less than sliding friction, the tyres are made circular instead of flat.