The car drove the first part of the path at a speed of 30 km / h, with what speed it traveled

| March 19, 2021 | education

The car drove the first part of the path at a speed of 30 km / h, with what speed it traveled the rest of the way if the average speed is 40 km / h.

To find out the speed of movement on the remaining part of the path, we apply the formula (we assume that Sн = Sо = S / 2): Vav = S / t = S / (S / 2Vн + S / 2Vо) = 1 / (1 / 2Vн + 1 / 2Vо), whence we express: 1 / Vср = 1 / 2Vн + 1 / 2Vо; 1 / 2Vo = 1 / Vn – 1 / 2Vn = 2Vn / (2 * Vn * Vcr) – Vcr / (2 * Vn * Vcr) = (2Vn – Vcr) / (2 * Vn * Vcr) and Vo = 2 * 2 * Vn * Vav / (2Vn – Vav) = 4 * Vn * Vav / (2Vn – Vav).

Data: Vн – speed on the first part of the track (Vн = 30 km / h); Vav – average speed (Vav = 40 km / h).

Let’s perform the calculation: Vo = 4 * Vn * Vav / (2Vn – Vav) = 4 * 30 * 10 / (2 * 30 – 40) = 1200/20 = 60 km / h.

Answer: The rest of the way, the specified car had to travel at a speed of 60 km / h.



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