When the bus is at a stop, a drop of rain leaves vertical tracks on the side window, and when it travels at a speed of 72

| February 16, 2021 | education

When the bus is at a stop, a drop of rain leaves vertical tracks on the side window, and when it travels at a speed of 72 km / h, the tracks of the drops are inclined to the vertical at an angle of 30. How fast are the drops of rain falling?

Vа = 72 km / h = 20 m / s.

∠α = 30 °.

Vk -?

Vka -?

If we assume that the drop relative to the ground moves uniformly in a straight line vertically downward, then, according to the law of relativity of velocities, we express the drop velocity by the formula: Vк = Vа / tgα.

Vk = 20 m / s / 30 ° = 35 m / s.

The speed of drops relative to the bus Vka will be determined by the formula: Vka = √ (Vk ^ 2 + Va ^ 2).

Vka = √ ((35 m / s) ^ 2 + (20 m / s) ^ 2) = 40 m / s.

Answer: the speed of the drop relative to the surface of the earth is Vк = 35 m / s, the speed of the drops relative to the bus is Vka = 40 m / s.



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