Chestermiller said:Work always depends on the reference frame.
Chet
Yes. You hit the nail on the head. Consider the case of a box on a conveyor belt, and the speed of the belt is increasing with time. So the frictional force is causing the box to accelerate, and the box is gaining kinetic energy. Now consider this same situation from the perspective of an accelerating frame of reference that is moving with the box. From this frame of reference, the frictional force is not doing any work, and the box is not accelerating. The frictional force is being balanced by the apparent horizontal body force acting on the box (associated with the acceleration).VictorH said:Why does work depend of the reference frame? If we do work isn't it the change of kinetic energy equal for all observers? The velocity vectors may change, of course, but the difference shouldn't for two inertial frames. Is it different for non-inertial frames?
Static friction is a type of force that occurs between two surfaces that are in contact with each other but not moving relative to one another. It prevents objects from sliding against each other when a force is applied.
Static friction does work by creating a counter force that opposes the applied force, thus preventing the object from moving. This allows the object to remain at rest or in a state of equilibrium.
The strength of static friction is affected by the nature of the surfaces in contact, the amount of force applied, and the roughness of the surfaces. The coefficient of friction, which is a measure of the frictional force between two surfaces, also plays a role.
Static friction occurs between two surfaces that are at rest, while kinetic friction occurs when the surfaces are in motion relative to each other. Static friction is typically stronger than kinetic friction, as it takes more force to overcome the initial resistance and start the motion between the two surfaces.
Yes, static friction can be beneficial in many situations. It allows us to walk without slipping, prevents objects from sliding off inclined surfaces, and helps vehicles to grip the road while braking. In some cases, static friction can also be used to our advantage, such as in the function of brakes in a car or the grip of a rock climber's shoes on the surface of a rock.