I keep getting “Normal force” questions wrong in Laws of Motion. What's the trap?
assuming the normal force always equals mg.
The usual trap: assuming the normal force always equals mg. How to avoid it: on an incline N=mg·cosθ, and it changes if there are extra vertical forces. Go back to the definition — the contact push a surface exerts perpendicular to itself.
Key point
Normal force
Common mistake
assuming the normal force always equals mg.
Memory tip
on an incline N=mg·cosθ, and it changes if there are extra vertical forces.
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