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A train starting from rest, picks up a velocity of 20m/s in 200s. It continues to move at the same rate for the next 500s and is then brought to rest in another 100s. Plot a v-t graph and calculate average velocity. |
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Answer» Answer: First let US plot the graph with the data given. Let the STARTING point be the origin in the speed - time graph. (a) Uniform rate of acceleration = slope of AB = (20−0) (m/s)/ [(200−0) s] = 0.1 m/s2. (b) Uniform retardation = − slope of CD = − (0−20)(m/s) /[(800−700)s] = 0.2 m/s2. (c) Total distance COVERED before stopping = area under the curve ABCD = area of ΔABE + area of rectangle BCFE + area of ΔCDF = ½ x 200 x 20 + 500 x 20 + ½ x 100 x 20 m = 2000 + 10000 + 1000 m = 13,000 m = 13 KM (d) Average speed = Total distance covered/total time taken = 13000 m /(800 s) = 16.25 m/s |
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