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# Physics Unit 4 - NEED HELP!!! watch

1. ) A satellite of mass 2520 kg is at a height of 1.39 × 107m above the surface of the
Earth. Calculate the gravitational force of the Earth attracting the satellite.

Right so this would require F= GMm/r^2, which had given me an answer of 2446N.

I need help on the second part which asks the following:

The satellite in part (b)(i) is in a circular polar orbit. Show that the satellite would travel
around the Earth three times every 24 hours.

-------------------------------------------------------------------------------------------------------------

So what I did was: http://prntscr.com/a41ms9 However I don't know whether doing this way is correct because in the mark scheme it isn't mentioned or I'm perhaps totally incorrect. Any help would be appreciated!
) A satellite of mass 2520 kg is at a height of 1.39 × 107m above the surface of the
Earth. Calculate the gravitational force of the Earth attracting the satellite.

Right so this would require F= GMm/r^2, which had given me an answer of 2446N.

I need help on the second part which asks the following:

The satellite in part (b)(i) is in a circular polar orbit. Show that the satellite would travel
around the Earth three times every 24 hours.

-------------------------------------------------------------------------------------------------------------

So what I did was: http://prntscr.com/a41ms9 However I don't know whether doing this way is correct because in the mark scheme it isn't mentioned or I'm perhaps totally incorrect. Any help would be appreciated!
How can you relate the period to the acceleration with circular motion formulas
3. (Original post by samb1234)
How can you relate the period to the acceleration with circular motion formulas
F = mw^2r, where w = omega = frequency = 2*Pi/T
However what I did in the screenshot was that valid or not?
F = mw^2r, where w = omega = frequency = 2*Pi/T
However what I did in the screenshot was that valid or not?
It's a very nice use of kepler's laws but it's validity is a different question. What you did is technically valid, but as far as an exam goes it's not how they will be wanting you to do it. It's one of those situations where your method is correct in terms of the physics used, but probably wouldn't be accepted by the examiner unfortunately.
5. (Original post by samb1234)
It's a very nice use of kepler's laws but it's validity is a different question. What you did is technically valid, but as far as an exam goes it's not how they will be wanting you to do it. It's one of those situations where your method is correct in terms of the physics used, but probably wouldn't be accepted by the examiner unfortunately.
I understand, by the way thanks for the quick response I really appreciate it man!
I understand, by the way thanks for the quick response I really appreciate it man!
No worries, what board are you doing?
7. (Original post by samb1234)
No worries, what board are you doing?
AQA
AQA
Same here, what are you aiming for?
9. (Original post by samb1234)
Same here, what are you aiming for?
Well, I'm currently finding this really difficult as I struggle to realize which equations to use and what principles to apply; also multiple choice questions are bloody hard haha. I hope to achieve a B...
10. (Original post by samb1234)
Same here, what are you aiming for?
Do you have any advice, I am currently taking notes from my textbook and revising that way, I do occasionally try find videos related to the topics; I attempt exam questions afterwards. Also what are you aiming for?
Do you have any advice, I am currently taking notes from my textbook and revising that way, I do occasionally try find videos related to the topics; I attempt exam questions afterwards. Also what are you aiming for?
Im going for a high a*, hopefully full ums but we'll see. Make sure you understand how to build equations rather than just the end result, so for your example its probably more beneficial if instead of memorising a result you use f=mw^2r and gravitation as that way you are building familiarity with them as you do it.

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