Gravitation and Orbit

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Gravitation• Any two bodies with mass some distance apart will attract each other with a force.

• 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:

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

Mm

r

GRAVITY IS ALSO

THE REASON WE HAVE

TIDES:

Orbits

This 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 Satellite

When 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 .

http://au.answers.yahoo.com/question/index?qid=20100701165924AAnFud5

This allows us to calculate how fast a satellite is travelling.

Fields Close 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.

Note: g is the strength of a gravitational field in this case, not the constant

Field Lines The 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.

The Time-Warp http://

upload.wikimedia.org/wikipedia/commons/7/78/GRACE_globe_animation.gif

The importance of gravity…

After years and years of relying on technology combined with the effects of microgravity, the humans have suffered severe bone

loss. After all, when the need for walking is eliminated, one doesn’t really need bones. Muscle loss is also apparent. Since they barely move, most of the muscle they have has atrophied. And the less muscle you have, the lower your metabolism,

and the slower you burn fat. Hence the fat blobs.