Motion in a straight line

Figure 2.15 gives a speed-time graph of
a particle in motion along a constant
direction. Three equal intervals of time
are shown. In which interval is the
average acceleration greatest in
magnitude? In which interval is the
average speed greatest ? Choosing the
positive direction as the constant
direction of motion, give the signs of v
and a in the three intervals. What are
the acceleration at the points A, B, C
and D ?