9th Class Science Sample Paper Sample Paper - 3 Term - 1

  • question_answer
      Answer the following questions (a) What are the differences between the terms 'distance' and 'displacement'? (b) An object has moved through a distance, can it have zero displacement? If yes, support your answer with an example. (c) A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus. Or Draw the velocity-time graph from the data given below
    Time(s) 2 4 6 8 10 12 14
    Velocity (m/s) 5 10 15 20 20 10 0
    (a) What type of motion is represented by the object during 0-6 seconds? (b) Find the acceleration in the first 6 seconds. (c) Using graph, calculate the distance travelled between 6 to 8 seconds. (d) Calculate retardation during 12-14 seconds.


      (a) The following table shows some differences between distance and displacement.
    S. No. Distance Displacement
    (i) Distance is the length of actual path travelled by a body, irrespective of its direction of motion. Displacement is the shortest distance between the initial and final positions of a body in a given direction.
    (ii) Distance between tow given points may be the same or different for different paths chosen. Displacement between two given points is always same.
    (iii) It is a scalar quantity. It is a vector quantity.
    (iv) Distance covered is always positive or zero. Displacement covered may be positive, negative or zero.
      (b) Yes, an object which has moved through a distance can have zero displacement. Suppose a person throws a ball upwards through a height hand catches back the ball. Then, distance covered by the ball = h + h = 2h Displacement of the ball = 0.                                                                                                                                                       (1) (c)                                                                                                                                                                    (1/2)                 Acceleration,                                                                                                                                                                                       (1/2) Or (1) (a) In time (0-2) s, motion is not defined. From 2 to 6 seconds, the motion is uniform.                                     (1) (b) It is constant during this time.                                                                                                                                                    (1) (c) Area below the graph in' 6 to 8 seconds, gives distance.                                                                                                                                                                                  (1) (d) Retardation                                                                                                                                                                                      (1)

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