differentiation Watch

KloppOClock
Badges: 14
Rep:
?
#1
Report Thread starter 3 weeks ago
#1
this feels like it should be easy but i am failing miserably at this.

I get given three equations.

E=-(gmn)/(2r)

v = squareroot[gn/r]

E' = -(v^3)2ap

i have to find a or p as a function of g,m,n and r.

E, v, p and r are dependent on time.
(v = r')

i have tried every single permutation of differentiation and substitution for the past 40 hours and still cannot do this.

please give me an idea of what the **** to do,

thanks
0
reply
mqb2766
Badges: 12
Rep:
?
#2
Report 3 weeks ago
#2
(Original post by KloppOClock)
this feels like it should be easy but i am failing miserably at this.

I get given three equations.

E=-(gmn)/(2r)

v = squareroot[gn/r]

E' = -(v^3)2ap

i have to find a or p as a function of g,m,n and r.

E, v, p and r are dependent on time.
(v = r')

i have tried every single permutation of differentiation and substitution for the past 40 hours and still cannot do this.

please give me an idea of what the **** to do,

thanks
Do you have a picture of the original question?
0
reply
KloppOClock
Badges: 14
Rep:
?
#3
Report Thread starter 3 weeks ago
#3
Name:  qqq.png
Views: 6
Size:  83.3 KB
0
reply
KloppOClock
Badges: 14
Rep:
?
#4
Report Thread starter 3 weeks ago
#4
(Original post by mqb2766)
Do you have a picture of the original question?
yeah sorry for the poor paint job
1
reply
mqb2766
Badges: 12
Rep:
?
#5
Report 3 weeks ago
#5
(Original post by KloppOClock)
Name:  qqq.png
Views: 6
Size:  83.3 KB
The first part says use (15), so just differentiate that using the chain rule?
0
reply
KloppOClock
Badges: 14
Rep:
?
#6
Report Thread starter 3 weeks ago
#6
(Original post by mqb2766)
The first part says use (15), so just differentiate that using the chain rule?
Name:  qa1.png
Views: 4
Size:  5.2 KB
i got this already, but i dont get how to use this to get rho or A as a function of GM, r and Me ?
0
reply
KloppOClock
Badges: 14
Rep:
?
#7
Report Thread starter 3 weeks ago
#7
(Original post by mqb2766)
The first part says use (15), so just differentiate that using the chain rule?
to be honest, i dont think i understand the question right. how can i find A as a function of variables when it is a given constant ? im not sure what im actually meant to be working out
0
reply
mqb2766
Badges: 12
Rep:
?
#8
Report 3 weeks ago
#8
(Original post by KloppOClock)
Name:  qa1.png
Views: 4
Size:  5.2 KB
i got this already, but i dont get how to use this to get rho or A as a function of GM, r and Me ?
I think the 2nd part is totally separate from the first part. Do you not just sub v into 18?
0
reply
KloppOClock
Badges: 14
Rep:
?
#9
Report Thread starter 3 weeks ago
#9
(Original post by mqb2766)
I think the 2nd part is totally separate from the first part. Do you not just sub v into 18?
idk what im meant to be finding. i already have dE/dt as a function of dr/dt. after that part in the second box im not sure what im meant to be getting.

by subbing in that v, i get dE/dT as a function of rho, A and E
0
reply
RDKGames
  • Community Assistant
Badges: 20
Rep:
?
#10
Report 3 weeks ago
#10
(Original post by KloppOClock)
Name:  qqq.png
Views: 6
Size:  83.3 KB
How is E_h different from E ? Partial derivative ??

What do these letters represent?
0
reply
mqb2766
Badges: 12
Rep:
?
#11
Report 3 weeks ago
#11
(Original post by KloppOClock)
idk what im meant to be finding. i already have dE/dt as a function of dr/dt. after that part in the second box im not sure what im meant to be getting.

by subbing in that v, i get dE/dT as a function of rho, A and E
I'm just about calling it a day, but I suspect that the aim is to get you to have dE/dt in two different forms and then equate them to get an expression for dr/dt. So I think the second part is simply subbing v into (18). The only part that sounds a bit confusing is why they have
h = r - R
There doesn't seem to be an h in the expressions, but I may be misunderstanding the notation.

Will look again in the morning.
0
reply
homemadeclock
Badges: 8
Rep:
?
#12
Report 3 weeks ago
#12
dE/dt = de/dr * dr/dt
0
reply
KloppOClock
Badges: 14
Rep:
?
#13
Report Thread starter 3 weeks ago
#13
(Original post by RDKGames)
How is E_h different from E ? Partial derivative ??

What do these letters represent?
theyre the same pretty sure
0
reply
homemadeclock
Badges: 8
Rep:
?
#14
Report 3 weeks ago
#14
(Original post by KloppOClock)
theyre the same pretty sure
Eh and E are similar, as Eh is total energy of the satellite at a hight and E is the total energy so where you have H=rh-re , rh is the radius of the orbit and re is the radius of the earth
Last edited by homemadeclock; 3 weeks ago
0
reply
homemadeclock
Badges: 8
Rep:
?
#15
Report 3 weeks ago
#15
so you have de/dt = Gmm/r^2 * dr/dt
then equate this to (18)
0
reply
homemadeclock
Badges: 8
Rep:
?
#16
Report 3 weeks ago
#16
also are you sure this is everything, i feel im not getting the full picture
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Edge Hill University
    Undergraduate and Postgraduate - Campus Tour Undergraduate
    Mon, 18 Feb '19
  • University of the Arts London
    MA Innovation Management Open Day Postgraduate
    Mon, 18 Feb '19
  • University of Roehampton
    Department of Media, Culture and Language; School of Education; Business School Undergraduate
    Tue, 19 Feb '19

Do you give blood?

Yes (37)
11.31%
I used to but I don't now (12)
3.67%
No, but I want to start (116)
35.47%
No, I am unable to (73)
22.32%
No, I chose not to (89)
27.22%

Watched Threads

View All