← Back to lesson

Relative motion: the general idea

Free notes · JEE Main Physics

Formulas

v⃗A/B=v⃗A−v⃗B\vec{v}_{A/B} = \vec{v}_A - \vec{v}_B

Relative velocity (vector)

Worked example

The acceleration of a body starting from rest is a = 2 m/s² for 4 s, then zero for 2 s. Find its velocity at t = 6 s.

  1. Area under the a–t graph = change in velocity.
  2. Area = 2 m/s² × 4 s = 8 m/s (the last 2 s add nothing).

Answer: 8