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# What is the missing force on this Free Body Diagram?

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• Newton's first law states that when viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.
Answer: 20 N Down.
According to Newton’s first law, since the object is at rest, the net force must be zero. Choose up as positive. So down is negative.
Net force $= 0 = 12 N + 8 N - \overrightarrow{F}$
$\Rightarrow \overrightarrow{F} = 20 N$ downwards.
answered Aug 19, 2014
edited Aug 19, 2014