Answer:
A. -30 N
Explanation:
not sure but if the box isn't moving then the force opposite of Polly would be equal to the force she's exerting.
The Ozone layer is responsible for the absorption of harmful
radiation from the sun before it hits the surface or exterior structure of our
planet. It is known to be a belt of a known occurring gas, known as “ozone”
which is sealed around the Earth’s atmosphere. It serves as a shield, which absorbs
most of the sun’s ultraviolet radiation.
The area between the 10 and the 12.
I attached the missing picture.
The force of seat acting on the child is a reaction the force of child pressing down on the seat. This is the third Newton's law. The force of a child pressing down the seat and the force of the seat pushing up on the child are the same.
There two forces acting on the child. The first one is the gravitational force and the second one is centrifugal force. In this example, the force of gravity is always pulling down, but centrifugal force always acts away from the center of circular motion.
Part AFor point A we have:

In this case, the forces are aligned, centrifugal is pointing up and gravitational is pulling down.
Part BAt the point, B situation is a bit more complicated. In this case force of gravity and centrifugal force are not aligned. We have to look at y components of this forces, y-axis, in this case, is just pointing upward.
Part CThe child will stay in place at point A when centrifugal force and force of gravity are in balance: