Help please! - Multiple Choice - Gravitational Fields

Watch
Jordan Jones
Badges: 0
Rep:
?
#1
Report Thread starter 5 years ago
#1
Mars has a diameter approximately 0.5 that of the Earth, and a mass of 0.1 that of the Earth.

Mars has a diameter approximately 0.5 that of the Earth, and a mass of 0.1 that of the Earth.
If the gravitational potential at the Earth’s surface is –63 MJ kg–1, what is the approximate value of the gravitational potential at the surface of Mars?

A: –13 MJ kg–1

B: –25 MJ kg–1

C:
–95 MJkg–1

D: –320 MJ kg–1

Reason for answer please?! Thanks!
0
reply
randlemcmurphy
Badges: 11
Rep:
?
#2
Report 5 years ago
#2
(Original post by Jordan Jones)
Mars has a diameter approximately 0.5 that of the Earth, and a mass of 0.1 that of the Earth.

Mars has a diameter approximately 0.5 that of the Earth, and a mass of 0.1 that of the Earth.
If the gravitational potential at the Earth’s surface is –63 MJ kg–1, what is the approximate value of the gravitational potential at the surface of Mars?

A: –13 MJ kg–1

B: –25 MJ kg–1

C:
–95 MJkg–1

D: –320 MJ kg–1

Reason for answer please?! Thanks!
Do you have an idea of how to start? We can work from there.
0
reply
Jordan Jones
Badges: 0
Rep:
?
#3
Report Thread starter 5 years ago
#3
(Original post by randlemcmurphy)
Do you have an idea of how to start? We can work from there.
The formulas given to us for Grav potential are:

(delta)W = m(delta)V

V = - GM/r

g = -(delta)V/(delta)r
0
reply
CaitlinDy
Badges: 9
Rep:
?
#4
Report 5 years ago
#4
So we know the formula for gravitational potential is V=-GM/r (symbols have their usual meaning)

Take all these values as 1 for Earth, -GM/r = -63 MJkg^-1

We also know that the mass of Mars is 0.1M and the radius is 0.5r

So put these values into the formula and you end up with V=0.2(-GM/r)

Since you are given the value of -GM/r, multiply it by 0.2 and you'll get the gravitational potential at the surface of Mars.

Hope this helps.
0
reply
randlemcmurphy
Badges: 11
Rep:
?
#5
Report 5 years ago
#5
(Original post by Jordan Jones)
The formulas given to us for Grav potential are:

(delta)W = m(delta)V

V = - GM/r

g = -(delta)V/(delta)r
I think you have to use the idea that V is directly proportional to M/r, do you know what to do then?
0
reply
Jordan Jones
Badges: 0
Rep:
?
#6
Report Thread starter 5 years ago
#6
(Original post by CaitlinDy)
So we know the formula for gravitational potential is V=-GM/r (symbols have their usual meaning)

Take all these values as 1 for Earth, -GM/r = -63 MJkg^-1

We also know that the mass of Mars is 0.1M and the radius is 0.5r

So put these values into the formula and you end up with V=0.2(-GM/r)

Since you are given the value of -GM/r, multiply it by 0.2 and you'll get the gravitational potential at the surface of Mars.

Hope this helps.
That helped a lot, thank you!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
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

Are you travelling in the Uni student travel window (3-9 Dec) to go home for Christmas?

Yes (91)
28%
No - I have already returned home (43)
13.23%
No - I plan on travelling outside these dates (62)
19.08%
No - I'm staying at my term time address over Christmas (32)
9.85%
No - I live at home during term anyway (97)
29.85%

Watched Threads

View All
Latest
My Feed