Equations of Uniformly Accelerated Motion
Free notes · JEE Main Physics
Formulas
The three kinematic equations
Displacement in the nth second (uniformly accelerated motion)
Key points
- Sign convention is everything. Choose a positive direction once, then u, v, a and s all carry signs. In free fall, a = −g when upward is positive — students who drop the minus sign lose the answer by 2×.
Worked example
A body starts from rest and accelerates uniformly at 2 m/s². Find (a) its velocity after 5 s, (b) the displacement in the 5th second.
- (a) v = u + at = 0 + 2 × 5 = 10 m/s
- (b) s_5 = u + (a/2)(2n − 1) = 0 + 1 × 9 = 9 m
Answer: v = 10 m/s; displacement in 5th second = 9 m