Forces on an incline
01 / 04 · Find only the real forces
Predict firstWith the block resting on the incline, does the normal force point straight up?
Red: gravity · Blue: normal force · Green: friction
Guided lesson
Tell real forces, components, and the friction threshold apart.
Prerequisites: A force has magnitude and direction; the net force determines acceleration, not velocity directly.01 / 04
Find only the real forces
Predict firstWith the block resting on the incline, does the normal force point straight up?
Gravity points straight down, the normal force is perpendicular to the contact surface, and friction runs along that surface. The normal force is not the reaction to gravity; both of them act on the block.
How to observe
- Rotate the scene and check the direction of the normal force
- Vary the incline angle and the friction coefficient
- Release the block and compare staying at rest with sliding
Model notes
An ideal rigid incline with g = 9.81 m/s². To keep the friction threshold in view, the static and kinetic coefficients share the single value μ; the block is released from rest. Components are not extra forces acting on the block.