A body accelerates uniformly from rest at 2$ms^{-2}$. Calculate its velocity when it has travelled a distance of 9m.

Analyze the question: A body starts from rest (u = 0) with uniform acceleration a = 2 m/s². We need its velocity v after travelling s = 9 m.

Concept: For uniform acceleration, use the equation of motion that links velocity, acceleration and distance without needing time:

v² = u² + 2as

Solution:

• u = 0 m/s
• a = 2 m/s²
• s = 9 m

v² = 0² + 2(2)(9) v² = 36 v = √36 = 6 m/s

Answer: The velocity is 6.0 m/s, which is option C.

Check: Time taken: s = ½at², so 9 = ½(2)t², giving t = 3 s. Then v = at = 2 × 3 = 6 m/s ✓.

Tip: When a question gives acceleration and distance but no time, go straight to v² = u² + 2as. "Starting from rest" means u = 0, which makes the calculation shorter. Also, 18 (option D) is a trap from just multiplying 2 × 9 without finishing the calculation (and forgetting the square root).