SPM Physics: AHA! Displacement ≠ Distance!

 

In circular motion problems, students often mistake distance traveled for displacement. But displacement is the straight‑line distance between the starting point and the ending point, not the length of the path.

Example:

A runner moves halfway around a circular track of radius

$63.6m$

.

• Distance traveled = half the perimeter =
  $200m$
  .

• Displacement = diameter =
  $2r=127.2m$
  .

Correct answer: 127.2 m.

Exam traps:

• Writing half the perimeter as displacement.

• Forgetting that displacement is a vector quantity.

• Ignoring that opposite points on a circle are separated by the diameter.

👉 Always check: Distance = scalar (path length). Displacement = vector (straight line).

AHA! Distance is path, displacement is direct. Not by sight, but by INSIGHT!

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