The discussion revolves around the direction of the friction force in a scenario involving a mass at rest on a spring on an inclined plane. Participants are exploring the conditions under which friction acts and its relationship to the motion of the mass.
The discussion is ongoing, with participants acknowledging the complexity of the situation. Some have provided insights into the nature of friction and its dependence on relative motion, while others emphasize the lack of sufficient information to reach a definitive conclusion about the direction of the friction force.
There is an indication that the problem may be constrained by insufficient details regarding the spring's state (tension or compression) and the mass's position relative to the spring. Participants note that without this information, the direction of friction cannot be conclusively determined.
Danya314 said:It could point either up the incline, or down the incline.
Danya314 said:So, which is it?
or in a direction to oppose motion. (It may be at rest.)Dick said:The force of friction always points opposite the direction the object is moving.
No, it opposes relative motion of the surfaces in contact. I know that's what you meant, but expressed the way you had it can lead to confusion, e.g. when a car is going uphill.Dick said:The force of friction always points opposite the direction the object is moving.
haruspex said:No, it opposes relative motion of the surfaces in contact. I know that's what you meant, but expressed the way you had it can lead to confusion, e.g. when a car is going uphill.
https://www.physicsforums.com/insights/frequently-made-errors-mechanics-friction/
Suppose there were no friction. Which way would the block move? Is there enough information to decide?Danya314 said:So in this case, would it point down the incline?
If a block, attached to a spring, is at rest on an inclined plane and that's all the information you have, then there is not enough information to deduce the direction of the friction force. It could be up the incline or down the incline, depending on the amount by which the spring is stretched or compressed. That's why I said your statement in the "attempt at a solution" section was correct.Danya314 said:So, which is it?
You wrote that it was "on" the spring. Is it above the spring or below it on the slope?Danya314 said:If friction was ignored, then I would assume the the net force would pull the block down the incline and strech the spring.