Science questions in short. [2 marks ]

It is due to continuous rubbing of soles with the ground, the spikes on the sole get damaged slowly and the soles become slippery.

To prevent slipping of the rope from hands, Preeti has to make her hands somewhat non-smooth, so she can rub her hands by introducing sand between them.

Marble will move the shortest distance on the layer of sand because it will exert a greater force of friction on the marble and other two surfaces like silk cloth and glass sheet will exert a lesser friction force comparatively.

When the car is at rest, we have to apply greater force because the value of static friction is more.
As the car starts moving, the friction changes into the rolling friction which is always less than the previous one. So, we have to exert the lesser force to keep it in motion.

The handle of a cricket bat or badminton racquet is rough, so that while playing, the bat or badminton racquet does not slip away from the hands of the player. Roughness is responsible for the frictional force without which gripping is not possible.

If the seat cover of rickshaw is very smooth, then the friction between our body and the seat is very small. Therefore, when the brakes are applied, we tend to slip.

No, the object will not experience any frictional force because to experience the force of friction, two surfaces must be there and there is only one surface in this case.

Due to the friction between knife and stone, the temperature of the knife and hence the stone increases and it increases to such a level that sparks are produced which can be seen while sharpening it.

Scientists got hints for the streamlined shapes from the body shapes of birds and fishes who have to move about in fluids all the time.

When the object is at rest, we have to apply more force to overcome interlocking between 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 block when it is already in motion.

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

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

Yes, there is always a force of friction between the wheels of a moving train and iron rails. The name of this friction is rolling friction, since the wheels are rolling on the track.
On introducing air cushion, the frictional force becomes less, since there is no contact between rails and wheels.

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.

Cartilage present in the joints of our body, reduces friction during movement of joints. But on wearing off this cartilage, the force of friction increases due to which the smoothness of movement decreases and one feels the joint pain.

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Both the friends can put rollers below the heavy load. Since, the rolling friction is smaller than the sliding friction. Therefore, putting rollers below the heavy load will make this task easier for them.

In many machines (like flour mills), belts are used to drive wheels for running the machines.
Greater friction is required between the belts and machine wheels, so that the belts can drive the machine wheels properly without slipping off wheels. So, in order to increase friction, machine belts are made up of special materials having rough surfaces.

After prolonged use, the mortar and pestle loose the roughness, due to which frictional force reduces and it does not work properly. So, we have to etch it to make it rough again.

i. Since, due to friction, a pencil writes on paper but there is smoothness on the surface of glass, a pencil cannot write on glass.
ii. If a pole is polished with grease, then the surface of pole becomes smoother thus reducing friction. So, climbing a greasy pole becomes tough.

The boy having the tyres which are old and used is most likely to slip because these tyres will experience less frictional force which is insufficient to move on the oily road.

The frictional force exerted by fluids is also called drag, When objects move through fluids, they have to overcome friction acting on them. In this process, they lose their energy. Efforts are made to minimise friction. So, objects are given special shapes and this type of shape is known as streamlined shape.

We know that friction is caused by the interlocking of irregularities in the two surfaces.
In case of static friction, interlocking between two objects is very strong but in case of sliding friction, there is a less time of getting interlocked with each other. Thus, the sliding friction is less than the static friction.

The heavy object will be pressed hard against the opposite surface and produces more friction. So, Seema will have to apply a larger force due to more friction

Sportsmen use shoes with spikes in order to avoid getting slipped in the field. The spikes in the shoes increase the friction, so they can run on the ground easily.

After spilling a bucket of soapy water on a marble floor, it would be more difficult for us to walk on the floor. Because the layer of soapy water reduces the friction and the foot cannot make a proper grip on the floor.

A book kept on a tilted writing desk starts sliding down. The direction of frictional force is in the opposite direction, thus frictional force will act in upward direction.