A boy throws a ball vertically upward with an initial velocity of 50 ms-1. What is the ve

Step 1: Identify given values and what to find
Given: u = 50 ms⁻¹ (upward), g = 10 ms⁻²
Find: Final velocity v when ball returns to ground

Step 2: Apply principle of energy conservation
For a projectile thrown upward and returning to same level, the final speed equals initial speed

Step 3: Alternative approach using kinematics
Formula: v² = u² + 2gh
Ball goes up to height h, then comes down same distance
For upward journey: 0 = 50² – 2(10)h, so h = 125 m
For downward journey: v² = 0 + 2(10)(125) = 2500
v = 50 ms⁻¹

Step 4: The answer is 50 ms⁻¹ (same magnitude as initial velocity)