A ball is projected vertically upward from ground level with an initial speed of 15ms−1.
(a) Taking upward as the positive direction and g=9.8ms−2, calculate:
(i) its velocity after 2s,
(ii) its displacement from the point of projection after 2s.
(b) Repeat the calculations in part (a) if downward is chosen as the positive direction, clearly showing how the signs of all quantities change.
(c) Compare the numerical answers obtained in both sign conventions and comment on the physical meaning of any negative value encountered.