A child starts from rest and moves with a constant acceleration of 3 m/s² for 4 s. He then walks at a constant speed for another 3 s. What is his total displacement?

Step-by-step solution

1. Step 1: Calculate displacement during acceleration using (s_1=ut+\frac12 at^2) with (u=0, a=3\text{ m/s}^2, t=4\text{ s}).
2. Step 2: Compute (s_1=0+\frac12\times3\times16=24\text{ m}).
3. Step 3: Find speed at the end of acceleration: (v=u+at=0+3\times4=12\text{ m/s}).
4. Step 4: Compute displacement during constant speed for 3 s: (s_2=v\times t=12\times3=36\text{ m}).
5. Step 5: Sum displacements: (24+36=60\text{ m}).
6. Step 6: State total displacement is 60 m.

Concept tested: displacement in uniform acceleration and constant speed

Published 16 October 2026 · How this solution was prepared and checked