Question

Following sets of three forces act on a body. Whose resultant cannot be zero?

• A. $10,10,10$
• B. $10,10,20$
• C. $10,20,20$
• D. $10,20,40$

Answer 1

The correct option is D $10,20,40$

$\text{Step 1: Conclusion from triangle law of addition}$

From the triangle law of vector addition,

The resultant must be zero if the sum of two forces $\ge$ remaining force

$\text{Step 2: Analysing options}$

In all the options except D, the sum of two forces is greater or equal to the remaining force

However, For option D, $10+20=30$

$30<40$

Hence, the resultant can not be zero for option D.

$\therefore$ Option $D$ is the correct answer.