Question

Problem 1 to 6: You are driving your brand new Mustang on a straight highway. Suddenly you felt a strong desire to check physics while driving and so you checked the gauge: It indicates that the speed is 80 kilometers per hour. You enjoyed driving for another hour while checking speeds. At the end of speeding up period of one hour, you read your car's speed as 160 kilometer per hour. Then suddenly you saw red and blue flashing light following you. 1. (a) Draw a graph of your car's speed over time using the grid below. You may assume the rate of speed gain stays the same over time for the whole period of one hour. Use the vertical axis for the speed and horizontal axis as time. 20 30 40 50 60

Answer 1

The acceleration of the car is: Av 160 - 60 km = 1.667 h min a = At 60 4. Remember that the average velocity is: . V +02 Vavg . 2 From the initial moment to 15 minutes: V1 = 607 V2 = V1 + at = (60) + (1.667)(15) = 85 Average velocity: 60 + 80 km Vavg= 2 = 0 h From the initial moment to 30 minutes: km V2 = 607 km V2 = V1 + at = (60) +(1.667)(30) = 110 Average velocity: 60 + 110 km Vavg==2 =857 From the initial moment to 45 minutes: km V1 = 607 V2 = va + at = (60) + (1.667)(45) = 135 ** Average velocity: 60 + 135 _ km Vavg = 2 = 97.57 From the initial moment to 60 minutes: km V60 km V2 = 60 h km v2 = V1 + at = (60) + (1.667)(60) = 160 Average velocity: km Vavg =2 =110 h 60+ 160 = 110

The distance is giving by the area below the graph: (v1 + 02) Ax = - 2 70*(15min) 60 min Ax = Vavgat From the initial moment to 15 min: km 1h = 17.5 km the initial moment to 30 min: km 1h = 42.5 km initial moment to 45 min: Ax = 97.5 the initial moment to 60 min: 1h Ax = 11 60 min .. = 110 km km (30min) 60 min 1h 19(45min) on 60 min = 73.125 km km 1 For a motion with constant acceleration: x = xo + vt + at In this case: Xe = 0 km km Vo = 60 n = min km a = 1.661hmin Then, the general equation is: x = 1t + 0.335t2 With t in minutes and x in km

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