A stone thrown at an angle of 30 ° to the horizon stayed in the air for 2 seconds. Determine the speed of the stone when it falls.

The movement time of a stone that was thrown at an angle to the horizon can be set by the formula:

t = 2V0 * sinα / g, where t is the given time of stone movement (t = 2 s), V0 is the initial velocity of the stone (m / s), α is the angle of throw to the horizon (α = 30º), g is the acceleration of gravity (g = 10 m / s2).

Let us express and calculate the speed of the stone at the moment of falling (equal to the initial speed):

t * g = 2V0 * sinα.

V0 = t * g / 2sinα = 2 * 10 / (2 * sin30º) = 20 m / s.

Answer: The speed of the stone when falling is 20 m / s.