9th Class Science Time and Motion

  • question_answer 8)
    The speed-time graph for a car is shown in the figure. (a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period. (b) Which part of the graph represents uniform motion of the car?

    Answer:

    The motion during first 4 seconds is not uniformly accelerated. So, distance travelled by car in first 4 seconds is calculated by graphical method. (a) Area of a small division on the graph     Total number of small divisions under the curve up to 4 s = 1615 Area under the curve up to     Therefore, the car has covered a distance of 17.2 m in first 4 s. (b) The limiting flat portion of the curve describes the constant speed of the car, i.e., a speed of 6.7 m  At this stage, the acceleration of the car is zero. Therefore, portion of the graph beyond 6.2 s describes the uniform motion of the car.


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