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nikolafmf
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I have read that static friction does no work and energy of the system is conserved if only this type of friction exists. Is this only an experimental fact, or can it be proved from basic principles? If it can, how?
Tipler, "Physics for Scientists and Engineers", 5th edition, page 292: "Because the friction is static, it does no work, and there is no dissipation of mechanical energy".maajdl said:Where have you read that static friction does no work?
... in the rest frame of the surfaces in contact.nikolafmf said:static friction does no work...
nikolafmf said:Tipler, "Physics for Scientists and Engineers", 5th edition, page 292: "Because the friction is static, it does no work, and there is no dissipation of mechanical energy".
The problem in question is ball rolling down an incline without slipping. The friction between the ball and the incline is said to be static.
Yes, or it is a (mis)interpretation of the "static" qualifier. In general "static friction" means there is no velocity difference between the contact surfaces, not that the contact is at rest.maajdl said:I think there is maybe a confusion here between "work" and "dissipation of energy.
Even in the ideal case work is done in any reference frame where the contact patch moves parallel to the force. Work is frame dependent.abitslow said:In the ideal case (which is no doubt what you are being taught) the atomic nature of the surfaces is NOT considered, hence no work is done.
It is rather well defined:craigi said:I'm not sure how well defined this is.
well, seeing as how there is only one force acting on the upper body, there's not a lot of room for arbitrariness there.craigi said:For example: Stack a rigid body on another rigid body on a frictionless surface and apply a gentle force to the bottom body. Work is done on the upper body but by which force? It seems arbitrary to me.
This and the choice of the reference frame of course. Once you decide what the bodies are and choose the reference frame, the rest follows.Nugatory said:The arbitrary choice was made when we considered this as two bodies with a force acting between them, instead of as one larger body.
Nice example!Nugatory said:If we had glued the two bodies together, we wouldn't have any trouble with treating the two bodies as one; and if we instead chose to treat them as two bodies, we'd have no difficulty seeing how the adhesive force of the glue is what's accelerating the upper body. We can think of static friction as just a rather weak glue.
Static friction is a type of force that occurs between two surfaces that are in contact with each other, but not moving relative to each other. It is a resistive force that prevents objects from sliding or slipping against each other.
Unlike kinetic friction, which occurs when two surfaces are in motion relative to each other, static friction only occurs when the surfaces are at rest. This means that the magnitude of static friction can vary, while kinetic friction remains constant.
Static friction does not do any work because it does not result in any displacement. Work is defined as the force applied to an object multiplied by the distance the object moves in the direction of the force. Since static friction does not cause any movement, no work is done.
The conservation of energy means that energy cannot be created or destroyed, only transferred or converted from one form to another. In the case of static friction, the energy of an object is not changing because no work is being done. Therefore, the energy is conserved.
Yes, static friction can do work in certain situations where it causes an object to move in the direction of the applied force. This can happen when the force applied is greater than the maximum static friction force, causing the object to overcome the resistance and start moving.