Science questions in short. [2 marks ]

The heels of the shoes get wear and tear first than the rest of the shoe sole. This is because, the heel of the shoe is interacted with the ground more than the other part and due to friction, the treads of the shoe sole wear out.

This is because the paper surface offers more friction to the pencil rubber when we rub on the paper, some bits of rubber come on the paper.

When a matchstick is rubbed on a rough surface, the surface produces friction. And we know friction produces heat, therefore the matchstick lightens up.

Lubrication means applying some additive to the parts of a machine to reduce the friction. Its important because it reduces the friction between the parts of the machine. But excess lubrication can generate more heat. Example- Castor Oil, Grease.

The brake pads of bicycles have to be replaced quite often because they gather more dirt, dust and the filthy matter on itself. So to allow proper functioning, they have to be replaced.

Wheels are important because they are used for transportation. Heavy machines can be moved from one place to another with the help of wheels because wheels can be rolled and the amount of force is also comparatively less.

When we apply brake sot the bicycle, a force of friction generates between the rim of the bicycle and the brakes. The friction is produced in opposite direction of motion. Thus, the bicycle is stopped.

By rubbing our hands against each other we create friction between our hands and this friction produces heat. Therefore, out hands become warm.

Castor oil and Grease are the two common lubricants. Note: A lubricant is a substance that smoothens a surface. It decreases the friction of a surface.

The smooth surface offers very less friction, due to which very less heat is produced by it and it is not sufficient to lighten up the matchstick.

While walking on the road, a man slips if he steps on a banana peel because the banana peel acts a lubricant between the road and the man’s shoe which reduces the friction. Thus, man slips on it.

A rough surface will cause more friction than a smooth surface. Because, rough offers more resistance to the other surface in contact as compared to the smooth surface.

The objects moving in fluids have streamlined shape so as to reduce the air drag or fluid friction that opposes their motion in any fluid.

It is easier to hold a kulhar (an earthen pot) because it more rough surface as it is made from mud. Mud offers more friction than glass and we are able to from a grip on the earthen plot.

Treads are made on the surface of tyres help in increasing the friction. These treads help in maintaining a firm grip on the road which reduces the risk of slipping on the road thus avoiding accidents.

The objects are built in special streamline shape to reduce the drag while moving in the air. Example, birds and Aeroplane have streamlined shapes.

When the engine of a car is switched off, then there is no energy available for the engine to oppose the frictional forces. Thus, the engine slows down and eventually comes to rest.