Test: Friction - 1

• A ball rolling on ground slows down and finally stops because of friction offered by the ground.
• Frictional force works in the opposite direction of motion to slow down the ball.

Friction always acts in the opposite direction to the motion, hence the force of friction will be from left to right.

Friction produces heat. When two moving surface are in contact of each other, they produce friction due to which heat is developed.
Example: Moving fans become hot due to this friction.

• Friction comes into play when irregularities present in the surfaces of two objects in contact get interlocked with each other.
• In sliding, the time given for interlocking is very small. Hence, the interlocking is not strong.
• Therefore, less force is required to overcome this interlocking. Because of this reason, sliding friction is less than static friction.

We sprinkle powder on carrom board to make the surface of the board smooth. This reduces the friction between the surface of the carrom board, the striker and the coins. As a result, the coins and the striker can move easily on the carrom board.

The substances that flow are called fluid. Liquid and gases are common fluid. Friction in fluid can be minimized by giving suitable shape as streamline to ships and airplanes.

A polished marble surface has the least frictional force, hence a car will travel farther on a marble floor.

In machine, friction between moving parts is reduced by using lubricants. These lubricants stick with machine parts to make them smoother that leads to reduction in friction.

Friction opposes the relative motion between two surfaces in contact. Frictional force acts in opposite direction of motion to slow down the speed of moving body.

• Fluid is a general term, that both liquid and gas fit under.
• A liquid has a definite volume and is incompressible.
• All liquids are fluids, but not all fluids are liquids.
• Therefore, fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids, etc.