Chapter 2 - Motion Along a Straight Line - Problems - Exercises - Page 59: 2.19

(a) $v_1 = 8.3 ~m/s$ (b) $a = 1.1~m/s^2$

(a) The average speed is $\frac{70.0 ~m}{6.00~s} = 11.67 ~m/s$ $\frac{v_1+v_2}{2} = 11.67 ~m/s$ $v_1 = (2)(11.67~m/s) - v_2$ $v_1 = (2)(11.67~m/s) - (15.0 ~m/s)$ $v_1 = 8.3 ~m/s$ (b) $a = \frac{\Delta v}{\Delta t} = \frac{v_2-v_1}{\Delta t}$ $a = \frac{15.0 ~m/s - 8.3~m/s}{6.00~s}$ $a = 1.1~m/s^2$