Answer
a) at t=4s, v=2.67cm/s
at t=7s, v=-1.33cm/s
b)a=-1.33cm/s^{2} for t=3,6,7s
Work Step by Step
At t=0s, v=8
t=6s, v=0
Gradient (m) = \frac{-8}{6}
at t=4, v=8-5.333=2.67cm/s
at t=7, v=-1.33cm/s
b) gradient of v-t graph = acceleration = -1.33cm/s^{2}
