Sample 1Medium
A velocity-time graph for a car moving along a straight road has time (s) on the x-axis and velocity (m/s) on the y-axis. The graph rises in a straight line from 0 m/s at t = 0 to 10 m/s at t = 4 s, stays flat at 10 m/s from t = 4 s to t = 8 s, and then falls in a straight line to 0 m/s at t = 10 s. What is the displacement of the car in the 10 s?
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The answer is A.
Displacement is the area under the v-t graph: triangle (1/2 × 4 × 10 = 20 m) + rectangle (4 × 10 = 40 m) + triangle (1/2 × 2 × 10 = 10 m) = 70 m.
- B.
80 m treats the last segment as 4 s long instead of 2 s.
- C.
60 m leaves out the final triangle (10 m) for the deceleration from 8 s to 10 s.
- D.
100 m is velocity × total time, as if the car moved at 10 m/s throughout.
NCERT: Class 11 Physics, Chapter 2