Artificial Gravity

1. Artificial Gravity

2. Central Force • There is no normal or tension force affecting things in orbit. • Like falling bodies that accelerate, a satellite accelerates toward the earth. • Gravity is a central force. orbital velocity centripetal acceleration Satellite Earth

3. Force on Mass • Newton’s law of acceleration applies to orbits. • Centripetal acceleration times mass is the force of gravity • The situation is the same for the satellite or any object in the satellite. Satellite or astronaut F a Earth

4. The net force of an object in circular orbit matches the centripetal acceleration. This is the same for a freely falling object. Velocity does not change the force or acceleration. Free Fall v Fnet a a = g Fnet = mg v Earth

5. Weightlessness • Objects in free fall exert no normal force. • Fnet = -ma = -mg + FN • If a = g, FN = 0 • The same is true in orbit. • Fnet = mar = Fgrav + FN • If ar = Fgrav/m, FN = 0 • Objects in orbit are weightless.

6. Spin the Station • A spinning station in orbit has a centripetal acceleration of its own. • Acceleration is on the inside pointing inward. • There is a corresponding centripetal force for object on the inside wall. Satellite a F

7. Station Gravity • The centripetal force is like an elevator accelerating upward. • Fnet = mar = FN • The net force must be due to a normal force. • Experience as weight • If rw2 = g then it matches earth’s gravity. Satellite a F

8. Centrifuge • A centrifuge spins to create an artificial gravity. • Liquid separation • Pilot training • Amusement rides

9. Gravitron • The Gravitron is an amusement ride that uses centripetal force. • Rotates at 24 rpm • Diameter is 14 m

10. Centripetal Correction • The spin of the earth creates a centripetal acceleration toward the axis of the earth. • The effect is like accelerating down in an elevator. • Items weigh less at the equator. a = w2r