SPM Physics: AHA! Lift Scale Reading = Normal Reaction

 

Why does the scale reading change in a lift?

• Stationary / uniform velocity:
  R=mg. Reading = actual weight.

• Accelerating upwards:
  R=mg+ma. Reading increases.

• Accelerating downwards:
  R=mg−ma. Reading decreases.

Exam tip: Always mention the direction of resultant force and use

F=ma. The scoring clue is: scale measures R, not mg.

This comic shows students that physics is about forces acting, not just memorising “weight.”

AHA! Lift scale reads R, not mg. Not by sight, but by INSIGHT!

#AHAPhysicsMoments #CikguLimCY #PhysicsInEverydayLife #100DaysOfPhysics #SeeWithPhysicsEyes #PhysicsWithInsight