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Equations of motion (constant acceleration)

Free notes · JEE Main Physics

Formulas

v = u + at,\quad s = ut + \tfrac{1}{2}at^2,\quad v^2 = u^2 + 2as

The three kinematic equations

Key points

Using these equations when acceleration is NOT constant is the most common marks-loser in kinematics.

Worked example

A car starts from rest and accelerates at 2 m/s² for 5 s. Find its final velocity and displacement.

u = 0, a = 2, t = 5.
v = u + at = 0 + 2×5 = 10 m/s.
s = ut + ½at² = 0 + ½×2×25 = 25 m.

Answer: v = 10 m/s; s = 25 m.