Question

which best explains why astronauts appear weightless when they are in a space shuttle orbiting earth?
they are falling toward earth at the same rate as the space shuttle
they are falling toward earth at a faster rate than the space shuttle
they are too far from earth to experience gravity.
they are too far from earth to experience air resistance

Explanation:

When astronauts are in a space shuttle orbiting Earth, they are in a state of free - fall. Since they and the shuttle are falling toward Earth at the same rate (due to the balance between the gravitational force pulling them down and their forward motion), there is no normal force acting on them (which is what we perceive as weight on Earth).
The second option is incorrect because if they fell faster than the shuttle, there would be a relative motion and they would not be in a stable "weightless" state within the shuttle.
The third option is wrong because gravity still acts on them at the altitude of the space shuttle (which is not extremely far from Earth in terms of gravitational influence).
The fourth option is not relevant to the concept of weightlessness in orbit; air resistance is not the cause of weight, and in orbit, the main factor is the gravitational and motion balance.

Answer:

They are falling toward Earth at the same rate as the space shuttle.