Answer:
a) 141.6m
b) 8.4m/s
Step-by-step explanation:
a) to find the total displacement you use the following formula for each trajectory. Next you sum the results:
![x_1=v_1t_1=(12m/s)(9s)=108m\\\\x_2=v_2t_2=(4.8m/s)(7s)=33.6m\\\\x_T=x_1+x_2=108m+33.6m=141.6m](https://img.qammunity.org/2021/formulas/physics/high-school/tqkqjs9a85xhyftscjqtnm6t049903kexn.png)
hence, the total distance is 141.6m
b) the mean velocity of the total trajectory is given by:
![v_m=(v_1+v_2)/(2)=(12m/s+4.8m/s)/(2)=8.4(m)/(s)](https://img.qammunity.org/2021/formulas/physics/high-school/wq5rplgwqosm2qgtcvg9on8be8pz7eabt8.png)
hence, the mean velocity is 8.4 m/s