A stunt woman of mass m falls into a net during the filming of an action movie. Assume she experiences upward acceleration magnitude aaa while touching the net. What is the correct expression for the normal force magnitude exerted on the stunt woman?
Consider upward as the positive direction.

The expression for the normal force exerted on her will m(a + g). That is,

N = m(a + g)

The Physics behind this scenario is Newton third law of motion which state that in every action, there is equal and opposite reaction.

The stunt woman of mass m will be falling under the gravity. Her acceleration a will be equal to gravitational acceleration g. When object falls under gravity, they will experience weightlessness because acceleration will be equal to acceleration due to gravity. That is, a = g

The downward force F on the woman will be equal to the product of her mass and the acceleration due to gravity. That is, F = -mg

Since we are considering upward as the positive direction, the downward will be negative direction.

The normal force N on her will be the opposite reaction of the downward force F. Since she experience an upward acceleration a, her normal force will be F = m(a + g)

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Therefore, the expression for the normal force exerted on her will m(a+g).  

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