An object in the vacuum of space orbits the earth at a fixed speed in a circular orbit several
hundred miles above the earth. What can we conclude about the reaction force?
a) That there is no reaction force-the net force on the object is zero, so the reaction
force is zero too.
b) The reaction force is a force that acts on the earth directed upward toward the object.
c) There is no reaction force- there’s a net force on the object, but zero reaction force because the
object is out in space.
d) The reaction force is a normal force that acts upward from the Earth’s surface.
The correct answer is option (b) - The reaction force is a force that acts on the earth directed upward toward the object.
To understand why, we need to recall Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. In this scenario, the object is orbiting the Earth due to the gravitational force exerted by the Earth on the object. According to Newton's third law, there must be an equal and opposite reaction force exerted by the object on the Earth.
The reaction force acts on the Earth and is directed upward toward the object. This is because the force of gravity between the Earth and the object is attractive, meaning it pulls the object toward the center of the Earth. As a result, there must be a corresponding reaction force that acts on the Earth, pushing it away from the object.
It's important to note that while the object is in orbit, its net force is not zero. The gravitational force provides the centripetal force required to maintain the circular motion of the object. However, the reaction force refers specifically to the equal and opposite force exerted on the Earth, not the net force acting on the object.