Question

Тело бросили с высоты 20 м. вертикально вверх со скоростью 20м/с. Найти время движения тела до поверхности.

Answer 1

Конечная скорость v = 0 м/с
полет вверх
h1 = (v^2 - v0^2) /2g = (0-20^2)  / 2*(-10) = -400 / -20 = 20 м
значит тело поднялось H=h1+h= (20+20)м на высоту H=40 м
теперь полет вниз
H = v*t +gt^2/2 
40 = 0*t + 10*t^2/2
40 = 5t^2
t^2 = 40/5 =8
t =√8 =2√2 = 2.8 c
ОТВЕТ  2.8 с

Answer 2

Calculation of Time of Motion

To find the time of motion of an object thrown vertically upwards from a height of 20 m with an initial velocity of 20 m/s, we can use the equation of motion:

h = v0t - (1/2)gt^2

Where: - h is the height of the object (20 m) - v0 is the initial velocity (20 m/s) - g is the acceleration due to gravity (approximately 9.8 m/s^2) - t is the time of motion (unknown)

To solve for t, we rearrange the equation:

t = (v0 ± √(v0^2 - 2gh)) / g

Substituting the given values:

t = (20 ± √(20^2 - 2 * 9.8 * 20)) / 9.8

Calculating the values inside the square root:

t = (20 ± √(400 - 392)) / 9.8

t = (20 ± √(8)) / 9.8

t = (20 ± 2.83) / 9.8

This gives us two possible values for t:

t1 = (20 + 2.83) / 9.8 ≈ 2.24 seconds

t2 = (20 - 2.83) / 9.8 ≈ 1.73 seconds

Therefore, the time of motion of the object until it reaches the surface is approximately 2.24 seconds or 1.73 seconds.