The x-t graph for motion of a car is given below
With reference to the graph, which of the given statement(s) is/are incorrect?

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The instantaneous speed during the interval t =5 s to t =10s is negative at all time instants during the interval.

The velocity and the average velocity for the interval t =0s to t =5 s are equal and positive.

The car changes its direction of motion at t =5 s.

The instantaneous speed and the instantaneous velocity are positive at all time instants during the interval t =0 s to t =5 s.

answer is A.

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Detailed Solution

The instantaneous speed is always positive as it is the magnitude of the velocity at an instant, so it is positive during t = 5 s to t =10 s.

For t = 0 s to t = 5 s, the motion is uniform and x-t graph has positive slope.

So, the velocity and average velocity, instantaneous velocity and instantaneous speed are equal and positive. During t = 0 s to t = 5 s, the slope of the graph is positive, hence the average velocity and the velocity both are positive.

During t = 5 s to t =10 s, the slope of the graph is negative, hence the velocity is negative. Since, there is a change in sign of velocity at t = 5 s, so the car changes its direction at this instant. Hence, option (a) is incorrect, while all others are correct.

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