Due to friction, the jar of a mixer becomes hot when it is run for few minutes.

Frictional force on an object in a fluid depends on the speed with respect to the fluid and the nature of fluid. It also depends on the shape of the object. e.g., all vehicles are designed to have shapes that reduce fluid friction.

(i) Rolling: The rolling wheels attached to luggage bags make it comfortable for passengers to carry them because rolling reduces friction and is smaller than sliding friction.
(ii) Sliding: By polishing surfaces or by applying a lubricant.

When a body rolls on other body, rolling friction comes into play.

The substances which reduce friction are called lubricants e.g., oil creams and grease.

(i) We sprinkle fine powder on carrom board to reduce friction.
(ii) Drops of oil are poured on the hinges of a door so that the door moves smoothly.

The treated tyres of cars and trucks provide better grip on the road.

There are three types of friction :
(i) Static
(ii) Sliding
(iii) Rolling

(i) Rolling friction,
(ii) Rolling friction,
(iii) Sliding friction,
(iv) Fluid friction,
(v) Sliding friction.

Sportsman uses shoes with spikes in order to avoid getting slipped in the field. The spikes in the shoes increase the friction, so he/she can run on the ground easily.

The frictional force acts in opposite direction of motion. So, on sliding book, the direction of friction force is upwards.

The roller provides rolling friction instead of sliding friction. Since, the rolling friction is very less than the sliding one, hence, even a child can pull such piece of luggage easily.

When the object is at rest, we have to apply more force to interlock the irregularities. On the other hand, when the object starts moving the contact points on its surface do not get enough time to lock into the contact points on the ground. So it is easier to move the box when it is already in motion.

Due to very less friction on wet and smooth floor, our foot cannot make exact grip with the floor. Thus, it is very difficult for us to walk on this floor.

As we step on a banana peel, then there is no grip between our foot and the banana peel due to very less friction. So, we slip accidentally.

No, because friction depends on the nature of surface in contact.

The object would never stop if there was no friction.

The arrow with a pointed tip suffers small air resistance due to its pointed shape, so it moves faster.

Frictional force always act in the direction opposite to the direction of motion, so it will act towards west.

Kabbadi players rub their hands with soil to increase the friction so that they can grip the opposite team players firmly.

No, we cannot eliminate friction completely because it is the characteristic property (molecular property) of material.

Oil, creams and grease when applied on a surface make it smooth, thus reduce friction, so these are called lubricants.

The substances that are used to reduce friction between two surfaces are called lubricants.

On rubbing the matchstick on a rough surface, the temperature increases due to friction, making the matchstick catch fire.

On a wet marble, floor, frictional force between the foot and floor decreases making it slippery, thus we feel difficult to move on a wet marble floor.

Yes, because friction acts only when two surfaces are in contact with each other.

No, friction can never be entirely eliminated. Some irregularities are always there.

In order to reduce single friction, pieces of luggage are fitted with rollers so that even a child can pull the luggage easily.

The rolling friction comes into play when one body rolls over the surface of another.

Friction is a necessary evil because it causes a lot of wear and tear.

If the two surfaces are pressed harder, then the force of friction will increase. So, it is easy to drag a carpet when nobody is sitting on it but when a person is sitting on it, then it produces more friction.

No, the force applied by both boys is equal. So, net force will be zero and hence friction force will not come into play.

Fishes are having streamlined shape, so they can move easily in the water.

Liquids and gases can flow and they do not have definite shape. So, they are called as fluid.

Streamlined shape is the special shape given to objects moving in fluids.

When an object moves in a fluid, then the resistance to the movement of object exerted by fluid is called fluid friction.

Yes, friction comes into play when two surfaces are in contact, e.g. glass and water in this case.

Due to friction, the jar of a mixture becomes hot when it is run for few minutes.

Rough surfaces have more irregularities.

Frictional force depends upon smoothness/roughness of surfaces and their mass.

Frictional force helps to write by chalk on blackboard.