write a note of 50 words why were the people of vermissa valley scared of the scowrers. The Valley of fear plz answer
Answers
Explanation:
Rolling friction is the friction between two surfaces when one or both are free to rotate rather than slide at the point of contact. It is caused by the fact that no surface is perfectly smooth and round and no material is perfectly elastic. Every small imperfection in the surfaces has to be either rolled over, or accommodated by the materials deforming, both of which consume energy.
Steel roller bearings are quite low in rolling friction, because they use a very elastic and stiff material rolling in very smooth cases made of a similarly stiff and elastic material. When loaded, the bearing surfaces don’t deform very much and because they have a high coefficient of elasticity, they return most of the energy to the surface, rather than absorbing it and heating up, although they do get hot over time.
Tyres, on the other hand, are quite high in rolling friction, because they’re made of a material that isn’t very stiff and is not so elastic, in order to be useable on the very imperfect surfaces of roads and provide the grip needed to resist sliding. Tyres these days are designed to be pressurised quite highly, which helps to reduce rolling friction by increasing the stiffness and the coefficient of elasticity.
A plain bearing or bush does not have rolling friction, because although one of the surfaces is rotating, the surfaces are sliding against each other, not rolling.
An object can be set into motion on a surface by different ways. The object may be pushed or pulled by a force such that only a particular surface is in contact with the mating surface on which it moves. In this case, the friction that resists the motion is called sliding friction. The another way is to make the object roll by placing it on circular wheels. In such a case, the friction gets reduced to a great extent, though, at the cost of additional weights of the carrier and its wheels. But, still a friction exists when the object is rolled on a surface. This type of friction is called Rolling Friction.
Rolling Friction Definition
A Rolling friction is a resistive force that opposes the rolling motion of an object. Rolling friction occurs when a round object rolls around a surface.One can obviously conclude by now that the study of rolling friction is limited to wheels or rollers and the surface on which they move. That is, for the same weight, the situation is same whether you put material A or material B on similar carriage and wheels.