Sensation of weightlessness homework

[ritwik06]

The sensation of weightlessness in a spacecraft in orbit is due to:
a) abscense of gravity
b)acceleration in orbit equal to acceleration due to gravity.
c)Shielding from gravity provided by spacecraft
d) spacecraft in orbit has no energy

I would mark a) right. do you agree?

 

[D H]

What do you think is keeping the spacecraft in orbit?

 

[ranger]

Weightless sensations exist when all contact forces are removed. Gravity is a non-contact force!

 

[Danger]

This would certainly appear to be a question from a school test, in which case it should be in the homework section. That having been said, your answer is wrong. The correct answer is very easy to establish if you pay attention to the circumstances outlined in the question. To start with, what is an 'orbit'?

 

[ritwik06]

What do you think is keeping the spacecraft in orbit?

The centripetal and centrifugal force, isn't it?

 

[ritwik06]

This would certainly appear to be a question from a school test, in which case it should be in the homework section. That having been said, your answer is wrong. The correct answer is very easy to establish if you pay attention to the circumstances outlined in the question. To start with, what is an 'orbit'?

An orbit is the path traced by a heavenly body while going around another massive heavenly body

 

[ranger]

The centripetal and centrifugal force, isn't it?

And how do we get centripetal force?

 

[ranger]

An orbit is the path traced by a heavenly body while going around another massive heavenly body

Okay, from that definition, is it possible for you to see why the answer you chose is wrong?

 

[D H]

Weightless sensations exist when all contact forces are removed. Gravity is a non-contact force!

There are two distinct things called "weight", both having units of force. One is the force on an object due to gravity, which is called the object's "actual weight". The other weight, "apparent weight", is what scales, accelerometers, and the otoliths in your inner ear measure. Weightlessness occurs when an object has negligble apparent weight.

I don't want to say much more until the original poster gets the right answer on his/her homework.

 

[D H]

Weightless sensations exist when all contact forces are removed. Gravity is a non-contact force!

This is not quite correct. Suppose I solidly embed an accelerometer in a metal sphere. Now suppose I charge the sphere and release it in a vacuum in which a strong static electrical field is present. The accelerometer will not sense the acceleration due to gravity but it will sense the acceleration due to the electrical field. No device can be constructed that directly senses gravitational acceleration. This is a consequence of the equivalence principle.

Weightless sensation exists when the acceleration of a body is equal to the acceleration due to the gravitation force on the body.

 

[ranger]

This is not quite correct. Suppose I solidly embed an accelerometer in a metal sphere. Now suppose I charge the sphere and release it in a vacuum in which a strong static electrical field is present. The accelerometer will not sense the acceleration due to gravity but it will sense the acceleration due to the electrical field. No device can be constructed that directly senses gravitational acceleration. This is a consequence of the equivalence principle.

Weightless sensation exists when the acceleration of a body is equal to the acceleration due to the gravitation force on the body.

What I was simply implying is that an object in free fall will have no apparent weight, since there is no contact with the surface and no normal or reaction force. The object does have actual weight which is the downward force upon the object by gravity. Hence an object in free fall has all contact forces removed where the only force gravity (non-contact) is acting on the object.