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3.The engine of a motorcycle can produce a maximum acceleration 5 m/s2. Its brakes can produce a maximunretardation 10 m/s2. What is the minimum time in which it can cover a distance of 1.5 km.A) 30 secB) 15 secC) 10 secD) 5 sec |
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Answer» The minimum time in which it can cover a total distance of 1.5km (= 1500m)is 30s you accelerate from rest during a time t ==> your speed = 5tthen you decelerate with an initial speed = 5t and a final speed = 0during a time T0 = 5t - 10T ==> t = 2T total distance must be 1500mdistance during acceleration = 5t²/2 = 10T²distance during deceleration = (5t)T - 10T²/2 = 10T²- 5T² = 5T²10T² + 5T² = 1500T² = 100T = 10s and t = 20stotal time = 30s ....ans |
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