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RATES ASSURED!!!!!!! WORK DONE BY STATIC FRICTION CAN BE NON ZERO?IS IT TRUE?( ITS GIVEN IN RESONANCE -RB)
Comments (4)
yes, it is true
for example-
Put your hand on a sheet of paper on the table, and move your hand along the table:
the sheet of paper will move together with your hand.
forces exerted on the paper-
vertical forces: gravity and the normal forces both from your hand and the table will cancel.
Horizontal forces are: the static friction arising from the interaction between your hand and the paper, and the force of kinetic friction coming from the interaction between the table and the sheet.
When the sheet (together with your hand) moves with constant velocity the forces of static and kinetic friction are of equal magnitude and as the force of kinetic friction is nonzero, so is the force of static friction.
The force of static friction between your hand and the sheet points forward, in the direction of motion. The force of kinetic friction between table and sheet points backwards.
and so the force of static friction exerted on the sheet of paper does work on the sheet. It is nonzero force, parallel to the displacement.
It is True,
Static friction
Static friction is friction between two solid objects that are not moving relative to each other. For example, static friction can prevent an object from sliding down a sloped surface. The coefficient of static friction, typically denoted as μs, is usually higher than the coefficient of kinetic friction.
The static friction force must be overcome by an applied force before an object can move. The maximum possible friction force between two surfaces before sliding begins is the product of the coefficient of static friction and the normal force: . When there is no sliding occurring, the friction force can have any value from zero up to . Any force smaller than attempting to slide one surface over the other is opposed by a frictional force of equal magnitude and opposite direction. Any force larger than overcomes the force of static friction and causes sliding to occur. The instant sliding occurs, static friction is no longer applicable—the friction between the two surfaces is then called kinetic friction.
An example of static friction is the force that prevents a car wheel from slipping as it rolls on the ground. Even though the wheel is in motion, the patch of the tire in contact with the ground is stationary relative to the ground, so it is static rather than kinetic friction.
The maximum value of static friction, when motion is impending, is sometimes referred to as limiting friction
Work of friction
In the reference frame of the interface between two surfaces, static friction does no work, because there is never displacement between the surfaces. In the same reference frame, kinetic friction is always in the direction opposite the motion, and does negative work. However, friction can do positive work in certain frames of reference. One can see this by placing a heavy box on a rug, then pulling on the rug quickly. In this case, the box slides backwards relative to the rug, but moves forward relative to the frame of reference in which the floor is stationary. Thus, the kinetic friction between the box and rug accelerates the box in the same direction that the box moves, doing positive work.
The work done by friction can translate into deformation, wear, and heat that can affect the contact surface properties (even the coefficient of friction between the surfaces). This can be beneficial as in polishing. The work of friction is used to mix and join materials such as in the process of friction welding. Excessive erosion or wear of mating surfaces occur when work due frictional forces rise to unacceptable levels. Harder corrosion particles caught between mating surfaces (fretting) exacerbates wear of frictional forces. Bearing seizure or failure may result from excessive wear due to work of friction. As surfaces are worn by work due to friction, fit and surface finish of an object may degrade until it no longer functions properly
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