Which of the following is not a type of friction?
Gravitational friction
Friction is the resistance offered at the contact between two surfaces when one tends to move or moves relative to the other. It is a surface/contact phenomenon and is conventionally classified according to the nature of that relative motion.
The genuine categories of friction include:
- Static friction — the resistance between two surfaces that are at rest relative to one another; it self-adjusts up to a limiting value before motion begins.
- Kinetic (dynamic/sliding) friction — the resistance when the surfaces are actually sliding over each other; usually a little less than the limiting static value.
- Rolling friction — the (much smaller) resistance experienced when a body such as a wheel or ball rolls over a surface.
- Fluid/film friction — the resistance arising in a lubricating film separating the surfaces.
By contrast, gravitational friction is not a recognised type of friction, so it is the odd one out and the correct answer. Gravity is a body force acting at a distance; it can produce the normal reaction that presses surfaces together (and thereby influences the friction force through F = μN), but gravity itself is not a contact resistance and does not constitute a class of friction.
- Static friction, kinetic friction, and rolling friction are all standard, well-defined types, so none of them is the answer.
Thus the term that is not a type of friction is gravitational friction.
Similar Questions
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With an increase in angle of the inclined surface, the maximum angle at which a body starts sliding down the plane is called ___________.
A block of weight (W) rests on a rough inclined plane with an angle of inclination α shown in the figure. The coefficient of friction between the block surface and the plane is μ, R is the normal reaction perpendicular to the inclined plane. A force (P) is applied parallel to the plane to prevent the block from sliding down. Which of the following represents the minimum value of (P) required to maintain equilibrium?
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Important Questions from Friction
A steel wheel of 600 mm diameter rolls on a horizontal steel rail. It carries a load of 500 N. The coefficient of rolling resistance is 0.3 mm. The force in N, necessary to roll the wheel along the rail is:
Which of the following option is CORRECT about the methods used to reduce the friction?
Which of the following is NOT a law of static friction?
If we push the break of car then car will begin to slide when:
An elephant is stopped by a rope wound twice around the rough trunk of a tree. If the elephant exerts a pull of 1000 kgf, the minimum force required to stop the elephant is_________. (Coefficient of friction between the rope and the tree is 0.3)
