Tag: merits and demerits of friction and methods to reduce it

The rough surface will increase the friction and so the rough surface of match box and match stick will produce more friction which helps in firing the stick easily.  

Correct air pressure helps in reducing deformation of the tyre and also provide an air cushion to reduce rolling friction. 

The friction will be more for more area of contact. Since the wheels have less area of contact so the friction will be less for them. 

Friction decreases with increase in temperature.

Answer is A.

Bearings reduce friction by providing smooth metal balls or rollers, and a smooth inner and outer metal surface for the balls to roll against. These balls or rollers 'bear' the load, allowing the device to spin smoothly.
The concept behind a bearing is very simple. Things roll better than they slide. The wheels on our car are like big bearings. If we had something like skis instead of wheels, our car would be a lot more difficult to push down the road.
That is because when things slide, the friction between them causes a force that tends to slow them down. But if the two surfaces can roll over each other, the friction is greatly reduced.

The carom board may sometimes be very rough. Sprinkling powder on a microscopic level, the powder particles offer rolling friction to the striker because of which the striker can be used for smooth and fast play.

The force of friction f is always opposite the direction the object that is moving . If the object would move, then the direction of the force of friction f will be opposite the movement. If the object would not move when there is no friction, then the force of friction is zero.Hence, though the surfaces of the object are rough the force of friction can be zero if the object would not move.

Answer is B.

The surface well powdered to stay away from harm to board surface due to scratch.It reduces the friction and helps in smoothing of the board and thereby allows the carom coins to go through in that flow which helps in fast play.
Powder is used in carom board for decreasing friction.

Friction depends upon mass and nature of the body of surfaces.
Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. However, friction decreases with smoothness only to a degree; friction actually increases between two extremely smooth surfaces because of increased attractive electrostatic forces between their atoms. 
Friction does not depend on the amount of surface area in contact between the moving bodies or (within certain limits) on the relative speed of the bodies. It does, however, depend on the magnitude of the forces holding the bodies together. 
When a body is moving over a horizontal surface, it presses down against the surface with a force equal to its weight, i.e., to the pull of gravity upon it; an increase in the weight of the body causes an increase in the amount of resistance offered to the relative motion of all the surfaces in contact.

Graphite is the only non-metal element that is a good conductor of electricity. Crystal structures rarely occur and easily break down. This is the reason for the material's greasy feeling despite being a dry lubricant.