Question need solution (1 Viewer)

[conman]

Can some one help me to solve this question?
http://img167.imageshack.us/my.php?image=physiceo6.png

 

[xiao1985]

gravitational field strength is proportional to inverse of radius squared , so the first graph should look some what like an inverse function...

2nd question, you can use constant = T^2/ R^3... which of course, means you will need radius of the earth...

 

[jyu]

Can some one help me to solve this question?
http://img167.imageshack.us/my.php?image=physiceo6.png

(a) Work out the area under the graph from h = 4x10^5 to h = 6x10^5. This give you the work required for each kg of the satellite.

:. total amount of work = area under graph x 800

(b) Use T^2/R^3 = t^2/r^3, where T period and R orbital radius of space shuttle, t period and r orbital radius of satellite

Notes: In using T^2/R^3 = t^2/r^3, the mass of the earth is not required.

T and t can be any unit as long as they are the same, also R and r can be any unit as long as they are the same.

R and r are measured from the centre of the earth, .: you need to know the radius of the earth.


:wave:

 

[jyu]

gravitational field strength is proportional to inverse of radius squared , so the first graph should look some what like an inverse function...

It appears straight because you are looking at comparatively short distance (a small section of the graph).

:wave:

 

[xiao1985]

It appears straight because you are looking at comparatively short distance (a small section of the graph).

:wave:

oops admittedly...

didn't see the question properly... i mistakenly thought the graph is a graph of GPE vs height...

(i blame it on lack of sleep and excess partying + alcohol)

 

[conman]

(a) Work out the area under the graph from h = 4x10^5 to h = 6x10^5. This give you the work required for each kg of the satellite.

:. total amount of work = area under graph x 800

(b) Use T^2/R^3 = t^2/r^3, where T period and R orbital radius of space shuttle, t period and r orbital radius of satellite

Notes: In using T^2/R^3 = t^2/r^3, the mass of the earth is not required.

T and t can be any unit as long as they are the same, also R and r can be any unit as long as they are the same.

R and r are measured from the centre of the earth, .: you need to know the radius of the earth.


:wave:

Where u get the formula total amount of work = Area under gaph x 800

I still don't get the relationship between area under the graph and the work required. I though the work done is equal to GPE, but they don't ask u to find GPE. That's reason why I still stuck at this question.:wave:

 

[xiao1985]

work = Force x distance

and gravitational field strength are as indicated... however, that's not the force on the satellite... the force is GFS x mass (ie, 800)

now, force changes as you go up... so what do you do? you integrate under the graph... which means finding the area under the graph...