Question

Under the influence of which set of forces among the options below can a body not be in equilibrium?

• A. $(3\text{N},4\text{N},8\text{N})$
• B. $(3\text{N},1\text{N},2\text{N})$
• C. $(3\text{N},4\text{N},5\text{N})$
• D. $(3\text{N},4\text{N},7\text{N})$

Answer 1

The correct option is A $(3\text{N},4\text{N},8\text{N})$

For a given set of forces to be in equilibrium, the resultant of any two forces should be equal to the third force.

Option $\left(a\right)$:
$8\text{N}\ne 4\text{N}+3\text{N}$ or

$8\text{N}\ne \sqrt{4^2+3^2}$ or

$4\text{N}\ne 8-3=5\text{N}$

Option $\left(b\right)$:
$2\text{N}=(3-1)\text{N}=2\text{N}$

Option $\left(c\right)$:
$5\text{N}=\sqrt{4^2+3^2}=5\text{N}$

Option $\left(d\right)$:
$4\text{N}=(7-3)\text{N}=4\text{N}$

Hence, option $\left(A\right)$ is the correct answer.