Question

Камень брошен вертикально вверх со скоростью 50 м/с. Через сколько секунд его скорость будет равна 30 м/с и направлена вертикально ВВЕРХ?

Answer 1

Выберем ось координат вертикально вверх, тогда проекции данных векторов V0x и Vx обе будут>0, т.к.тело брошено вверх, а проекция ускорения свободного падения gx<0, т.к. вектор направлен вниз.
gx=(Vx-V0x)/t, t=(V-V0)/(-g)=(30-50)/(-10)=2c - искомая величина.
 

Answer 2

Problem Analysis

We are given that a stone is thrown vertically upwards with an initial velocity of 50 m/s. We need to determine how many seconds it will take for the stone's velocity to become 30 m/s and be directed vertically upwards.

Solution

To solve this problem, we can use the equations of motion for uniformly accelerated motion. The equation that relates the final velocity (v), initial velocity (u), acceleration (a), and time (t) is:

v = u + at In this case, the stone is thrown vertically upwards, so the acceleration is due to gravity and is equal to -9.8 m/s^2 (taking downward as the positive direction). We can rewrite the equation as:

v = u + (-9.8)t

We are given that the initial velocity (u) is 50 m/s and the final velocity (v) is 30 m/s. Substituting these values into the equation, we have:

30 = 50 + (-9.8)t

Simplifying the equation, we get:

-20 = -9.8t

Dividing both sides by -9.8, we find:

t = -20 / -9.8

Simplifying further, we get:

t ≈ 2.04 seconds

Therefore, it will take approximately 2.04 seconds for the stone's velocity to become 30 m/s and be directed vertically upwards.

Answer

The stone's velocity will be equal to 30 m/s and directed vertically upwards after approximately 2.04 seconds.