A ball rolls down an inclined track as shown in given figure. Is its motion, a straight-line motion? Assuming the starting point of the ball (O) to be the origin, can its motion from O to D be depicted using a horizontal line as shown in the figure? Are the values of total distance travelled and magnitude of displacement from O equal or different at positions A, B, C and D?    [Pg. No. 51]

Yes, the motion of the ball is a straight-line motion because it moves along a straight inclined track from O to D. Taking O as the origin, the motion can be represented on a horizontal line as shown, since only the distance from the starting point is considered. At positions A, B, C and D, the total distance travelled and the magnitude of displacement are equal because the ball moves only in one direction along a straight path without changing direction.