Science Chapter 1: Motion Question Answers

                                              Motion 

                                      NCERT Questions

Q1.An object has moved through a distance.Can it have zero displacement? If yes, support your answer 

      with an example.

Ans.Yes,an object can have zero displacement even when it has moved through a distance.This happens when final position of the object coincides with its initial position.For example,in going from home to school and coming back to home,some distance is travelled but displacement is zero.

Q2.A farmer moves along the boundary of a square field of side 10 m in 40 s.What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds?

Ans.In fig. 1, ABCD is a square field of side 10 m.

       Time for one round = 40 seconds,

       Total time = 2 Minutes 20 seconds = (2 x 60 + 20)s = 140 s

       Number of rounds completed =140/40 = 3.5

       If farmer starts from A, he will complete 3 rounds (A==>B==>C==>D==>A) at A. In the last 0.5 

       round starting from A, he will finish at C.

                                  =>                                                              

       Displacement = AC , Where AC = root of AB^2 + BC^2
                                                        = root of 10^2 + 10^2= 10 root of 2m


Q3.Which of the following is true for displacement?
(a) It cannot be zero
(b)Its magnititude is greater than the distance travelled by the object.
Ans.Displacemment can be zero.The statement is not true.
(b).Magnitude of displacement is never greater than the distance travelled by the object.The statement is
     not true.

Q4.Distinguish between speed and velocity.
Ans.Velocity:
       It is speed in a particular direction

       Velocity = Displacement  ÷ Time

       Speed:

       It is a distance travelled by an object per unit time

       Speed = Distance ÷ Time

Q5.Under what conditions is the magnititude of average velocity of an object equal to average speed?

Ans.When a body moves along a straight line, the magnitude of average velocity of an object is equal to its average speed.

Q6.What does the odometer of an automobile measure?

Ans.The odometer of an mobile measures the distance travelled by the vehicle.

Q7.What does the path of an object look like when it is uniform motion ?

Ans.In uniform motion,the path of an object can be straight line, curved line,zig-zag line, or even a circle.It can have any shape.This is because in uniform motion, speed is constant. The direction of motion may change.

Q8.When will you say a body is in (i) uniform acceleration ? (ii) non uniform acceleration ?

Ans.(i) A body is said to be in uniform acceleration, when velocity of the body changes by equal amounts in equal intervals of time. For example, motion a a body falling freely under gravity.

(ii) A body is said to be in non acceleration, when velocity of the body changes by unequal amounts in equal interval of time. For example, motion of a car on highway through city limits.

Q9.What is the nature of the distance time graphs for uniform and non uniform motion of an object ?

Ans.When the motion is uniform,the distance time graph is a straight line with some slope.

        When the motion is non uniform, the distance time graph is not a straight line.It can be any curve.

Q10.What can you say about the motion of an object whose distance time graph is a straight line parallel to the time axis ?

Ans.When distance time graph of an object is a straight line parallel to the time axis, distance of the object at every instant of time is the same. there the object must be stationery.