Nope any formulas not on the sheet they provide, must be derived or you will lose marks
In question 26c of the 2015 HSC, the answers expected you to calculate orbital velocity by using Centripetal Force = Gravitational Force and then manipulating the equation in terms of velocity. Can you not just use the formula Orbital V = sqrt(GM/r) that's taught in the course immediately instead of deriving this equation from Fc and Fg?
https://gyazo.com/fe725781429d1fc417b88457b4844ad6
Last edited by Sp3ctre; 26 Oct 2017 at 2:58 PM.
2017 HSC:: English Adv - Maths Ext 1 - Maths Ext 2 - Chemistry - Physics
2017 ATAR: 93.6 (screw English)
2018: UNSW BE ME Electrical Engineering
Nope any formulas not on the sheet they provide, must be derived or you will lose marks
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The formula for orbital velocity isn't provided in the formula sheet though, so you're supposed to derive the equation to show the markers where the formula came from. That's what I've always been taught to do, anyway. Not sure if you'll get marks deducted for not doing it or not though.
Oh, guess you do lose marks then.
Thanks for the replies
2017 HSC:: English Adv - Maths Ext 1 - Maths Ext 2 - Chemistry - Physics
2017 ATAR: 93.6 (screw English)
2018: UNSW BE ME Electrical Engineering
Yeah, you need to derive it from scratch. This applies for escape velocity as well. It should be pretty straightforward anyway; takes literally 3 lines.
For orbital velocity (you must have the first line as well):
Fc = Fg
mv²/r = GmM/r²
v = sqrt (GM/r)
For escape velocity (include first line):
KE ≥ GPE
½mv² ≥ GmM/r (comparing just the magnitudes)
v ≥ sqrt (2GM/r)
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