Question

A 0.2 kg object at rest is subjected to a force $\left(0.3\hat{i}-0.4\hat{ j}\right)$ N. What is the velocity after 6 s?

• A. $\left(9\hat{i}-12\hat{ j}\right)$
• B. $\left(8\hat{i}-16\hat{ j}\right)$
• C. $\left(12\hat{i}-9\hat{ j}\right)$
• D. $\left(16\hat{i}-8\hat{ j}\right)$

Answer 1

Answer: (A)

Here, $m = 0.2 \,kg, u = 0$
$\vec{F}=\left(0.3 \hat{i}-0.4 \hat{j}\right)$
$\vec{v}$ = ?, $t = 6 \,s $
$\vec{a}=\frac{\vec{F}}{m}=\frac{\left(0.3 \hat{i}-0.4 \hat{j}\right)}{0.2}=\left(\frac{3}{2} \hat{i}-2 \hat{j }\right)$
From $\vec{v}=\vec{u}+\vec{a} t$
$\vec{v}=0+\left(\frac{3}{2} \hat{i}-2 \hat{j }\div \right)\times6=9 \hat{i}-12 \hat{j}$