The discussion centers on the concept of uniform circular motion in a vacuum, specifically regarding a pencil spun in space without gravity or air resistance. Participants confirm that the pencil would continue to spin indefinitely due to the conservation of angular momentum, as no external forces act on it after the initial spin. The centripetal force required for circular motion does not do work on the pencil, allowing it to maintain its motion. Additionally, while classical physics suggests perpetual motion is impossible, the conversation clarifies that the pencil's motion is not a perpetual motion machine, as it does not perform useful work.
PREREQUISITESPhysics students, educators, and anyone interested in the principles of motion and energy conservation in isolated systems will benefit from this discussion.
sophiecentaur said:Whatever forces are acting, no energy is 'consumed' or transferred if there is no movement in the direction of those forces (i.e. the string / pencil gets no longer or shorter). Work done is Force times Distance moved in the direction of the force.
ViolentCorpse said:The distance covered is circular, so isn't there even some component of distance being covered in the direction of the centripetal force?