-
Start with Newton's 1st Law. The spaceship is moving in a curved path and Newton says for that to happen there must be a force (Gravity) causing the ship to move in a curved path. (We can say the ship is "falling" toward the earth, but because of its forward motion (Tangential Velocity) it travels in curved path that never reaches the earth. Think of throwing a baseball the faster you throw it the farther it goes before it hits the ground. So, you keep throwing faster and faster and you get to a speed that the ball goes all the way around the earth. Though it was falling. The falling part is why the path is curved and the ball goes around the earth.
Another way to look at this that might make more sense:
I am a heretic. Purists say there is no such thing as centrifugal force. There is, you just introduce a Rotating Frame of Reference. Because:
"A rotating reference frame can have advantages over an inertial reference frame.[15][4] Sometimes the calculations are simpler (an example is inertial circles), and sometimes the intuitive picture coincides more closely with the rotational frame (an example is sedimentation in a centrifuge). By treating the extra acceleration terms due to the rotation of the frame as if they were forces, subtracting them from the physical forces, it's possible to treat the second time derivative of position (relative to the rotating frame) as if it was the absolute acceleration. Thus the analysis using Newton's law can proceed as if the reference frame was inertial, provided the fictitious force terms are included in the sum of forces. For example, centrifugal force is used in the FAA pilot's manual in describing turns.[16] Other examples are such systems as planets, centrifuges, carousels, turning cars, spinning buckets, and rotating space stations."
http://en.wikipedia.org/wiki/Centrifugal…
Centrigugal Force is the REACTION FORCE to the CENTRIPETAL FORCE (Gravity)
Reaction Forces MA part of F = MA. The spaceship has mass and is being accelerated by gravity(The Action Force or Centripetal Force). As required by Newton's 3rd Law, there is an equal and opposite Reaction Force (Centrifugal Force).
Since Centripetal and Centrifugal are equal and opposite, there is no Net Force on the spaceship or the astronauts inside. Thus, they are "Weightless."
Another way to look at this that might make more sense:
I am a heretic. Purists say there is no such thing as centrifugal force. There is, you just introduce a Rotating Frame of Reference. Because:
"A rotating reference frame can have advantages over an inertial reference frame.[15][4] Sometimes the calculations are simpler (an example is inertial circles), and sometimes the intuitive picture coincides more closely with the rotational frame (an example is sedimentation in a centrifuge). By treating the extra acceleration terms due to the rotation of the frame as if they were forces, subtracting them from the physical forces, it's possible to treat the second time derivative of position (relative to the rotating frame) as if it was the absolute acceleration. Thus the analysis using Newton's law can proceed as if the reference frame was inertial, provided the fictitious force terms are included in the sum of forces. For example, centrifugal force is used in the FAA pilot's manual in describing turns.[16] Other examples are such systems as planets, centrifuges, carousels, turning cars, spinning buckets, and rotating space stations."
http://en.wikipedia.org/wiki/Centrifugal…
Centrigugal Force is the REACTION FORCE to the CENTRIPETAL FORCE (Gravity)
Reaction Forces MA part of F = MA. The spaceship has mass and is being accelerated by gravity(The Action Force or Centripetal Force). As required by Newton's 3rd Law, there is an equal and opposite Reaction Force (Centrifugal Force).
Since Centripetal and Centrifugal are equal and opposite, there is no Net Force on the spaceship or the astronauts inside. Thus, they are "Weightless."