In a race, usain bolt accelerates at 1.99m/s^2 for the first 60.0m, then decelerates at -0.266m/s^2 for the final 40.0m. what was his final velocity? (unit = m/s)

14.7 m/s

Explanation:

During the first phase, given:

Δx = 60.0 m

v₀ = 0 m/s

a = 1.99 ms²

Find: v

v² = v₀² + 2aΔx

v² = (0 m/s)² + 2 (1.99 m/s²) (60.0 m)

v = 15.5 m/s

During the second phase, given:

Δx = 40.0 m

v₀ = 15.5 m/s

a = -0.266 ms²

Find: v

v² = v₀² + 2aΔx

v² = (15.5 m/s)² + 2 (-0.266 m/s²) (40.0 m)

v = 14.7 m/s

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.