-981N would be the reaction force of a person be that stands completely still with a mass of 100 kg.
An opposing force to an action force is referred to as a reaction force. The response force that results from surface engagement and adhesion while sliding is known as friction. Usually, the activities of applied forces result in reaction forces and reaction moments.
As,
F = ma
where, F = force
m = mass of object
a = acceleration due to gravity
Plugging in the values we get,
F = 100kg × 9.81m/s
F = 981 N
Since, reaction force acts opposite to action force so the correct answer is -981N.
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