• Support PF! Buy your school textbooks, materials and every day products via PF Here!

How high above the the earth's surface is the meteor?

  • Thread starter fa08ti
  • Start date
32
0
a 12 kg meteor experiences an acceleration if 7.2 m/s^2. when falling towards the earth

a: how high above the the earth's surface is the meteor?
b: what force will a 30 kg meteor experience at the same altitude?

attempt:

i'm, not sure which equation to use..would it be
v= sqrt(Gm/r)?
 
302
0
Re: meteor

You need a formula which relates acceleration due to the earth's gravity and the distance from it's center. Do you know such a formula?
 
32
0
Re: meteor

would this be correct?

gh = GM / (R + h )2
 
302
0
Re: meteor

If R is the radius of the earth, and h above the surface of the earth, yes.

[itex]g=\frac{GM}{(R+h)^{2}}[/itex]
 
32
0
Re: meteor

i used the formula and got a negative value?
 
Last edited:

Dick

Science Advisor
Homework Helper
26,255
618
Re: meteor

i used the formula and got a negative value?
How did you get a negative value? g should come out to 9.8m/s^2 if h=0. Do you know why? To get 7.2m/s^2, h should certainly be positive.
 
32
0
Re: meteor

i used the mass of the meteor and i think i should have used the mass of earth?
 

Dick

Science Advisor
Homework Helper
26,255
618
32
0
Re: meteor

thanks..i just want someone to clarify something..does the mass of the object not matter? if so, why not?
 

gneill

Mentor
20,488
2,610
Re: meteor

thanks..i just want someone to clarify something..does the mass of the object not matter? if so, why not?
The mass of the object does not matter. Every mass falls with the same acceleration (in a given gravitational field).

[tex] F = G\frac{M m}{r^2} [/tex]
but [itex] F = m a[/itex] so that [itex] a = F/m[/itex] Thus

[tex] a = \frac{F}{m} = G\frac{M}{r^2} [/tex]

Only the mass of the Earth, M, matters for the acceleration of mass m in its field (that's the acceleration with respect to the Earth, of course).

So, why should this be so? It is so because inertial mass happens to be equal to gravitational mass for any object with mass (Look up "equivalence principle").
 
32
0
Re: meteor

thanks everyone sooo much
 

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top