The boat is moving along the river. The speed of the river is 7.2 km / h, the speed of the boat relative

| July 5, 2021 | education

The boat is moving along the river. The speed of the river is 7.2 km / h, the speed of the boat relative to the water is 7 m / s. What is the speed of the boat relative to the shore?

VT = 7.2 km / h = 2 m / s.

Vk / t = 7 m / s.

Vк -?

VT = 7.2 km / h = 7.2 * 1000 m / 1 * 3600 s = 2 m / s.

According to the law of relativity of motion, the speed of a body relative to a stationary coordinate system (relative to the coast) is the vector sum: the speed of the moving coordinate system relative to the stationary one (the speed of the current relative to the coast) and the speed of the body relative to the moving coordinate system (the speed of the boat relative to the water).

Since the boat moves with the current, the speed of the boat relative to the coast Vk is the sum of the current velocity Vt and the speed of the boat relative to the water Vk / t: Vk = Vt + Vk / t.

Vk = 2 m / s + 7 m / s = 9 m / s.

Answer: the speed of the boat relative to the coast is Vк = 9 m / s.



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