Question

A body of velocity 5 m / s towards north and its velocity becomes 10 m / s towards south

in time 3 s. Magnitude of average acceleration is :

• A. $\frac{5}{3}$ m/ s${}^2$
• B. $\frac{2}{3}$ m/s${}^2$
• C. 5 m/s ${}^2$
• D. None of these

Answer 1

The correct option is C 5 m/s ${}^2$

Denote north by $\hat{j}$ and south by $-\hat{j}$

we get velocities as $v_1=5\hat{j}$ and $v_2=-10\hat{j}$

so $change$ in the velocity will be $v_2-v_1=-10\hat{j}-5\hat{j}=-15\hat{j}$

cosidering only value we get $\Delta v=15m/s$

the average accleration will be $a=\frac{15m/s}{3s}=5m/s^2$