Weightlessness in Satellites

by • 04/07/2012 • GeneralComments (0)600

Weightlessness in Satellites

An apparent loss of weight experienced by a body in a spacecraft in orbit is called weightlessness.

To discuss weightlessness in artificial satellites, let us take the example of an elevator having a block of mass ;m; suspended by a spring balance attached to the coiling of the elevator. The tension in the thread indicates the weight of the block.

Consider following cases.

1. When Elevator is at Rest

T = m g
2. When Elevator is Ascending with an Acceleration ‘a’

In this case

T > m g

Therefore, Net force = T – mg

m a = T – m g

T = m g + m a

In this case of the block appears “heavier”.
3. When Elevator is Descending with an Acceleration ‘a’

In this case

m g > T

Therefore

Net force = m g – T

m a = m g – T

T = m g – m a

In this case, the body appears lighter
4. When the Elevator is Falling Freely Under the Action of Gravity

If the cable supporting the elevator breaks, the elevator will fall down with an acceleration equal to ‘g’

From (3)

T = m g – m a

But a = g

Therefore

T = m g – m g

T = 0

In this case, spring balance will read zero. This is the state of “weightlessness”.

In this case gravitation force still acts on the block due to the reason that elevator block, spring balance and string all have same acceleration when they fall freely, the weight of the block appears zero.

Artificial Gravity

In artificial satellites, artificial gravity can be created by spinning the space craft about its own axis.

Now we calculate frequency of revolution (v) of a space craft of length 2R to produce artificial gravity in it. Its time period be ‘T’ and velocity is V.

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