The body moves at a speed of 15 km / h for 30 minutes. After changing the speed, it moves for another 1 hour.
| January 17, 2021 | education
The body moves at a speed of 15 km / h for 30 minutes. After changing the speed, it moves for another 1 hour. The average body speed is 10 km / h. Find the path covered by the body in 1 hour.
Initial data: t1 (first time of movement) = 30 min (0.5 h); V1 (first speed) = 15 km / h; t2 (second time of movement) = 1 h; Vav. (average body speed) = 10 km / h.
The speed of the body on the second section of the path is expressed from the formula for calculating the average speed: Vav. = S / t = (S1 + S2) / (t1 + t2) = (V1 * t1 + S2) / (t1 + t2), whence V1 * t1 + S2 = Vav. * (t1 + t2) and S2 = Vav. * (t1 + t2) – V1 * t1.
Calculation: S2 = 10 * (0.5 + 1) – 15 * 0.5 = 7.5 km.
Answer: The body covered 7.5 km in 1 hour.
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