With what speed must an object be thrown to reach a height of 400m. assume negligible air resistance.

Final velocity(v)² - Initial Velocity(u)² = 2 * acceleration due to gravity(g) * height(h)

While the object will attain its maximum height the final velocity will be 0 m/s

0² - u² = 2 * -9.8 * 91.5

-u² = -1793.4

u² = 1793.4

u = √1793.4

u = 42.35(appx)m/s

=42.35 * 2.23 mi/s

=94.44 mi/s(appx)

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i don't understand. explain it clearly