Answer:
person a₁ = -0.625 m / s², box a₂ = 0.0714 m / s²
Step-by-step explanation:
In this exercise we have a problem of action and reaction forces, the force with which the person (action) pushes the box is of the same magnitude as the force with which the box (reaction) pushes the person, but in the opposite direction.
We work that body separately
Person
-F = m₁ a₁
a₁ = -F / m₁
a₁ = -50.0 / 80.0
a₁ = -0.625 m / s²
the negative sign means that the person moves away from the box
Box
F = m₂ a₂
a₂ = F / m₂
a₂ = 50.0 / 700
a₂ = 0.0714 m / s²