# If a ball thrown vertically upward falls to the ground after 3 s, then the speed of the ball at the moment of falling is …

January 30, 2021 | education

| The origin of the coordinate system is at the point where the ball is thrown. The Y-axis is directed upwards.

The Y coordinate became zero after 3 s.

Expression for Y coordinate:

Y = V₀t – gt² / 2.

The same expression for t = 3 s:

0 = V₀ * 3 s – (10 m / s² * 3² c²) / 2;

V₀ * 3 c = 45 m;

V₀ = 15 m / s.

The speed at the moment of falling is:

V = V₀ – gt = 15 m / s – 10 m / s² * 3 s = -15 m / s (minus sign, because the velocity vector is directed downward).

The absolute value of V is 15 m.

Answer: 15 m / s.

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