(i) Define instantaneous velocity of an object whose displacement from the origin at time t seconds is given by s=s(t) metres.
(ii) Explain, with reasons, how the sign (positive or negative) of the instantaneous velocity obtained in part (i) indicates the direction of motion of the object along the straight line.
(iii) Illustrate your explanation by considering the displacement function s(t)=7−4t metres and commenting on the object’s motion for t>0.