Answer:
This may refer to a situation like:
"one person pushes a box, if there is equal and opposite reaction why the box moves and the person does not?"
Remember the second Newton's law:
F = m*a
suppose that the mass of the person is 3 times the mass of the box.
So, if the box has a mass M, the person will have a mass 3*M
Then the Newton's equation for the box when the person pushes with a force F is:
F = M*a
solving for the acceleration, we get:
F/M = a
While the person is also pushed by the box with a force with the same magnitude, then the equation for the person is:
F = (3*M)*a'
Solving for the acceleration, we get:
F/(3M) = a'
Now we can compare the acceleration of the box (F/M) with the acceleration of the person (F/3M).
Is easy to see that the acceleration of the box is 3 times the acceleration of the person.
So regardless of the fact that both the box and the person experience a force with the same magnitude, the box will move more due to this force.
This is why in situations like this, the forces do not seem balanced.
