Science M.C.Q. [I MARKS]

Friction does wear and tear of the objects.

Sound is produced due to increased frictional force between the two surfaces. Oil is used as a lubricant to reduce frictional force in machines.

When a car moves, air resists its motion. As a result, cars are designed in streamline shapes. Streamline shapes of cars ensure that this air resistance is minimized.

A force of friction arises when two objects move in contact with each other. The opposing force that acts on an object that is moving in a fluid (air) is called drag. An object that is moving in air must overcome this opposing drag. The presence of drag reduces the speed. The magnitude of drag depends on the shape of the object. Drag is the minimum when the moving object is of streamline shape. In the given situation, the shapes of all four cars are different. Therefore, the fuel consumption in each will be different because each will be opposed by different drags. Greater the drag, more is the fuel required to move the car a certain distance and vice-versa. Here, only car III is streamline in shape. Therefore, it will experience least amount of drag against its motion. As a result, it will consume less fuel as compared to the other cars in covering the same distance.

Tread in tyre of vehicle increases resistance with the road to prevent skidding. To dry the hands by applying a coarse material increases the friction. Saliva reduces the friction in mouth so that food can be easily swallowed. Powder can reduce the friction so that gloves of the surgeon can be easily pulled.

Friction is the force that generates due to the interlocking of irregularities present between two surfaces in contact. The generation of this friction in between the surfaces of joints of the door is responsible for the noise. Therefore, to reduce this sound, the friction must be reduced by applying some lubricant over the joints. A lubricant will form a thin layer in between the moving surfaces to reduce the friction and hence, to reduce the noise. Grease is used as a lubricant. Hence, to reduce the noise of the door, Atul should lubricate the joints with grease.

The frictional force between the surface and the nail opposes the motion of the nail toward the magnet. The nail moves easily if this frictional force becomes less. Frictional force is less on an oily surface as compared to the force of friction on a cemented, carpeted, or sandy surface. Therefore, the distance d will be relatively large for an oily surface.

Sliding friction is required to keep the object moving with the same speed. Once the applied force overcomes the static friction, the object starts moving.

In a mechanical system, friction opposes motion between different parts of the system. Work is done against these frictional forces. Hence, heat energy is produced by the system.

Friction is a kind of force that always acts against the direction of movement of a body. As a result of the friction between the box and the surface, mechanical energy gets converted into heat energy. This heat energy raises the temperature of the bottom of the box.

When muscular force is applied by Thaddeus in the form of pedaling, the bicycle moves. When he stops pedaling, the frictional force between the tires and the ground slows the bicycle. The direction of the frictional force is opposite to the direction of motion of the bicycle. Hence, the speed of the bicycle decreases.

A body shape which offers very little resistance to the flow of a fluid around it, is called streamlined shape.