Gravitation and Orbit describes the basics of gravitation and orbits. Any two bodies with mass attract each other with a gravitational force proportional to their masses and inversely proportional to the distance between them. Orbits occur as objects fall towards a central body but have enough tangential velocity to miss it and continue falling indefinitely. The speed of satellites in orbit can be calculated based on their distance and the gravitational force exerted by the central body. Gravity also causes tides on Earth and gravitational fields can be approximated as uniform close to the surface, becoming stronger closer to the source mass. Prolonged time in microgravity conditions like space can lead to severe bone and muscle loss in humans.

1. Gravitation and Orbit

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3. GravitationAny two bodies with mass some distance apart will attract each other with a force.

4. This force is the gravitational force, it is dependent on the mass of the two bodies and the distance between them. The strength of the gravitational force is described thusly: 𝐹𝑔=𝐺𝑀𝑚𝑟2

5. Where G is gravitational constant, M and m are larger and smaller masses and r is the distance between them. rMm

6. GRAVITY IS ALSO THE REASON WE HAVE TIDES:

7. OrbitsThis is one of a few common ways of understanding orbits:As the object moves sideways (tangentially), it falls toward the central body. However, it has enough tangential velocity to miss the orbited object, and will continue falling indefinitely.Speed of a SatelliteWhen objects are in orbit they are held, at a distance, by a gravitational force. This force supplies the centripetal force they need to travel in a circle so 𝐹𝑔=𝐹𝑐. 𝐺𝑀𝑚𝑟2=𝑚𝑣2𝑟𝑣= √(𝐺𝑀𝑟)http://au.answers.yahoo.com/question/index?qid=20100701165924AAnFud5This allows us to calculate how fast a satellite is travelling.

8. FieldsClose to the Earth we can approximate the field as uniform, it is actually radial.Because each kg of mass feels a weight we can use this to find g. The weight felt is equal to the strength of the force of the gravitation. 𝑊=𝐹𝑔𝑚𝑔=𝐺𝑀𝑚𝑟2𝑔=𝐺𝑀𝑟2Note: g is the strength of a gravitational field in this case, not the constant 9.8𝑚𝑠−2

9. Field LinesThe closer (more dense) the field lines are the stronger the field is.Field lines are radial but at the surface of the Earth the field is approx. uniform.

10. The Time-Warphttp://upload.wikimedia.org/wikipedia/commons/7/78/GRACE_globe_animation.gif