Question

A body is at rest under the action of three forces, two of which are $\overrightarrow{F_1}=4\hat{i},\overrightarrow{F_2}=6\hat{j}$, the third force is

• A. $4\hat{i}+6\hat{j}$
  
• B. $4\hat{i}-\hat{j}$
  
• C. $-4\hat{i}+6\hat{j}$
  
• D. $-4\hat{i}-6\hat{j}$

Answer 1

The correct option is D $-4\hat{i}-6\hat{j}$

$F_1+F_2+F_3=0\Rightarrow 4\hat{i}+6\hat{j}+F_3=0\therefore \overrightarrow{F_3}=-4\hat{i}-6\hat{j}$