Answer
(a) $a_{av}=2~m/s^{2}$
(b) $a_{av}=0$
(c) $a_{av}=-0.5~m/s^{2}$
Work Step by Step
(a) The segment A begins with $t_{0}=0,~v_{0}=0$. It finishes with $t_{1}=5~s,~v_{1}=10~m/s$
$a_{av}=\frac{\Delta v}{\Delta t}=\frac{v_{1}-v_{0}}{t_{1}-t_{0}}=\frac{10~m/s-0}{5~s-0}=2~m/s^{2}$
(b) The segment B begins with $t_{1}=5~s,~v_{1}=10~m/s$. It finishes with $t_{2}=15~s,~v_{2}=10~m/s$
$a_{av}=\frac{\Delta v}{\Delta t}=\frac{v_{2}-v_{1}}{t_{2}-t_{1}}=\frac{10~m/s-10~m/s}{15~s-5~s}=0$
(c) The segment C begins with $t_{2}=15~s,~v_{2}=10~m/s$. It finishes with $t_{3}=25~s,~v_{3}=5~m/s$
$a_{av}=\frac{\Delta v}{\Delta t}=\frac{v_{3}-v_{2}}{t_{3}-t_{2}}=\frac{5~m/s-10~m/s}{25~s-15~s}=\frac{-5~m/s}{10~s}=-0.5~m/s^{2}$
