4.5.3—Forces

Forces arise from interactions such as weight, contact, tension, friction or thrust. A complete free-body diagram lets ΣF=ma be applied without double-counting.

Name the body, draw force directions and distinguish applied forces from resultant shorthand. Resolve only after the physical forces are identified.

For a block pulled by a rope on a rough plane, include weight, normal reaction, tension and friction before resolving along the plane.

Centripetal force is not an extra force; it is the name for the resultant inward force in circular motion.