Why is the person not staying stationary in the air when there is equal forces from both sides?
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1$\begingroup$ Zero net force doesn't mean zero velocity. It means constant velocity, including zero velocity. $\endgroup$– David WhiteCommented Jul 29, 2023 at 17:13
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3 Answers
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Equal forces only means the person is not accelerating. Per Newton's 1st law, an object at rest or moving at constant speed in a straight line remains at rest or moving at constant speed in a straight line unless acted upon by a net force. The person is moving at constant speed so the net force acting on the person is zero. In this case the upward air drag force equals the downward force of gravity.
Hope this helps.
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No, if the forces are balanced then there will be no net acceleration.
"Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. " So if there is no net force, the oject will stay in motion.
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$$ ma = F$$ $$ m\ddot h = F_{tot} = F_g + F_{air} $$ $$ m\ddot h = -mg + c\dot h^2 $$
so
$$ \ddot h = 0$$
means
$$ mg = c\dot h^2 $$ of:
$$ \dot h = v = \sqrt{mg/c}$$
where $c$ is some kind of drag coefficient.
