Chapter 2 - Kinematics: Description of Motion - Learning Path Questions and Exercises - Exercises - Page 61: 30

$a). -19.44 m/s$ $b). 2.78 \,m/s^{2}$

a). $35km/hr = 35 \times \frac{1000m}{3600s}=9.722 m/s$ Now, $S=-9.722 \times 7 m = -68.054 m$ $v^{2}=u^{2}+2aS$ $0=u^{2}+2\times \frac{v-u}{t} \times S$ $0=u^{2}-2\times \frac{0-u}{7} \times 68.054$ $u=-19.44m/s$ b). Acceleration = $\frac{v-u}{t}=\frac{0-(-19.44)}{7}=2.78 m/s^{2}$