The velocity−time plot for a particle moving on a straight line is shown in the figure:
Calculate the average speed of the particle in the time interval 10−20s.
A
20m/s
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B
−20m/s
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C
10m/s
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D
−10m/s
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Solution
The correct option is C10m/s Given:
To calculate the average speed between 10−20s, we need to first make sure the acceleration of the body is constant.
Since it is a continuous straight-line from 0−20s, the acceleration of the body is indeed constant and is equal to −20−1020=−1.5m/s2
At t=10s, the magnitude of the velocity = speed = 0m/s
At t=20s, the magnitude of the velocity = speed = 20m/s
The average speed is 0+202=10m/s
[This method of obtaining the average speed works only when the acceleration of the body is constant in the given time interval.]