Worksheet on friction for class 8

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Worksheet on friction for class 8 

´╗┐Friction class 8. Download Worksheet on friction for class 8 including fill up, answer in one word, long questions and more based on latest CBSE syllabus.

Friction class 8 (Points to remember)

Friction is the force that opposes the motion when two surfaces are in contact, move or tend to move with respect to each other.

Rolling Friction is the friction experienced by a body when it rolls over the surface of another.

Sliding Friction is the friction experienced by a body when it slides over the surface of another.

Friction is caused by the irregularities on the two surfaces in contact. Even those surfaces which appear very smooth have a large number of minute irregularities on them. Irregularities on the two surfaces lock into one another. When we attempt to move any surface, we have to apply a force to overcome interlocking. On rough surfaces, there are a larger number of irregularities. So the force of friction is greater if a rough surface is.

We see that the friction is caused by the interlocking of irregularities in the two surfaces. It is obvious that the force of friction will increase if the two surfaces are pressed harder. If an object started moving, it would never stop if there were no friction. Had there been no friction between the tyres of the automobiles and the road, they could not be started or stopped or turned to change the direction of motion. On the other hand, friction is evil, too. It wears out the materials whether they are screws, ball bearings or soles. Friction can also produce heat. Vigorously rub your palms together for a few minutes.

You might have observed that the jar of a mixer becomes hot when it is run produces heat. In fact, when a machine is operated, heat generated causes much wastage of energy.

We deliberately increase friction by using brake pads in the brake system of bicycles and automobiles. friction in order to increase efficiency. When oil, grease or graphite is applied between the moving part of a machine, a thin layer is formed there and moving surfaces do not directly rub against each other Interlocking of irregularities is avoided to a great extent. Movement becomes smooth. The substances which reduce friction are called lubricants.

When one body rolls over the surface of another body, the resistance to its motion is called rolling friction. Rolling reduces friction. It is always easier to roll than to slide a body over another. That is the reason it is convenient to pull luggage fitted with rollers. Since the rolling friction is smaller than the sliding friction, sliding is replaced in most machines by rolling by the use of ball bearings. Common examples are the use of ball bearings between hubs and the axles of ceiling fans and bicycles. 

The frictional force exerted by fluids is also called drag. The frictional force on an object in a fluid depends on its speed with respect to the fluid. The frictional force also depends on the shape of the object and the nature of the fluid.

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