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ICSE-IX-Physics

02: Motion in One Dimension

with Solutions -

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    Section : A

  • Qstn #1
    Differentiate between the scalar and vector quantities, giving two examples of each.
    Ans :

    Scalar
    		 Vector
    They are expressed only by their magnitudes.
    		 They are expressed by magnitude as well as direction.
    They can be added, subtracted, multiplied or divided by simple arithmetic methods.
    		 They can be added, subtracted or multiplied following a different algebra.
    They are symbolically written by English letter.
    		 They are symbolically written by their English letter with an arrow on top of the letter.
    Example: mass, speed
    		 Example: force, velocity


  • Qstn #2
    State whether the following quantity is a scalar or vector?

    (a) Pressure

    (b) Force

    (c) Momentum

    (d) Energy

    (d) Weight

    (d) Speed
    Ans :

    a) Pressure is a scalar quantity.

    b) Momentum is a vector quantity.

    c) Weight is a vector quantity.

    d) Force is a vector quantity.

    e) Energy is a scalar quantity.

    f) Speed is a scalar quantity.



  • Qstn #3
    When is a body said to be at rest?
    Ans :

    A body is said to be at rest if it does not change its position with respect to its immediate surroundings.


  • Qstn #4
    When is a body said to be in motion?
    Ans :

    A body is said to be in motion if it changes its position with respect to its immediate surroundings.


  • Qstn #5
    What do you mean by motion in one direction?
    Ans :

    When a body moves along a straight line path, its motion is said to be one-dimensional motion.


  • Qstn #6
    Define displacement. State its unit.
    Ans :

    The shortest distance from the initial to the final position of the body is called the magnitude of displacement. It is in the direction from the initial position to the final position.

    Its SI unit is metre (m).


  • Qstn #7
    Differentiate between distance and displacement.
    Ans :

    Distance
    		 Displacement
    It is a scalar quantity.
    		 It is a vector quantity.
    The distance is the length of path travelled by the body.
    		 The displacement is the shortest length in direction from initial to the final position.
    It is always positive.
    		 It can be positive or negative depending on the direction of the body.
    Can be more than or equal to the magnitude of displacement.
    		 Can be less than or equal to the distance, but never greater than the distance.

  • Qstn #8
    Can displacement be zero even if distance is not zero? Give one example to explain your answer.
    Ans :

    Yes, displacement can be zero even if the distance is not zero.

    For example, when a body is thrown vertically upwards from a point A on the ground, after sometime it comes back to the same point A. Then, the displacement is zero, but the distance travelled by the body is not zero (it is 2h; h is the maximum height attained by the body).


  • Qstn #9
    When is the magnitude of displacement equal to the distance?
    Ans :

    The magnitude of displacement is equal to the distance when the motion is in a fixed direction.


  • Qstn #10
    Define velocity. State its unit.
    Ans :

    The velocity of a body is the distance travelled per second by the body in a specified direction.

    Its SI unit is metre/second (m/s).


  • Qstn #11
    Define speed. What is its S.I. unit?
    Ans :

    The speed of a body is the rate of change of distance with time.

    Its SI unit is metre/second (m/s).


  • Qstn #12
    Distinguish between speed and velocity.
    Ans :

    Speed
    		 Velocity
    Scalar quantity
    		 Vector quantity
    Rate of change of distance with time
    		 Rate of change of displacement of a body with
    time
    Speed is always positive-it is the magnitude of velocity.
    		 The velocity is given a positive or negative sign depending upon its direction of motion.
    Average speed is never zero.
    		 Average velocity can be zero
    When the body returns to its initial position, speed will not be zero.
    		 When the body returns to its initial position, velocity can be zero.

  • Qstn #13
    Which of the quantity speed or velocity gives the direction of motion of body.
    Ans :

    Velocity gives the direction of motion of the body.


  • Qstn #14
    When is the instantaneous speed same as the average speed?
    Ans :

    Instantaneous velocity is equal to average velocity if the body is in uniform motion.


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