Physics Problem Involving Gravitational Force on an object based on R

AI Thread Summary
To determine the distance r inside the Earth where the gravitational force equals that at r = 4RE, the assumption of uniform density is crucial. The initial approach using conservation of energy to equate gravitational potential energies was deemed ineffective. Instead, applying Gauss's Law is suggested, despite the user not being familiar with it. The discussion highlights the need to consider gravitational force and potential rather than electric force concepts. A resource link was provided to assist in understanding the application of these principles.
taylorkrauss
Messages
4
Reaction score
0

Homework Statement



At what distance r inside the Earth is the gravitational force due to Earth the same as at
the distance r = 4RE (where the latter distance is clearly outside Earth)? Assume uniform
density of Earth.


Homework Equations



conservation of energy? TME = GPE + KE



The Attempt at a Solution



At first I thought I could do conservation of energy and set both GPE's equal to each other and solve for a new Radius, but this is not working out well. Is there something I need to do involving the density of Earth and the mass? I really have no idea. Thanks for any help!
 
Physics news on Phys.org
Energy conservation doesn't appear relevant to me... I'd go with Gauss.
 
Hmm...I haven't learned Gauss's Law though. This wants Gravitational Force and Gravitational Potential not Electric Force and EPE, so I'm not sure how I'd apply Gauss (after googling, I saw it was a theroem for electric potential). How would you go about using Gauss's Law?
 
That was perfect! Thank you!
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Calculating Tidal Range (Gravitation)
Replies
12
Views
2K
What is the mass of the Galaxy's core?
Replies
10
Views
1K
Gravitational Field Multiple Choice Help
Replies
5
Views
2K
Is potential energy defined only for internal conservative forces?
Replies
15
Views
1K
Calculating Energy Ratios: Moving Mass to and from Earth's Core
Replies
2
Views
1K
Why does the gravitational force decrease below the Earth's surface?
Replies
10
Views
3K
Calculate the gravitational force exerted on a 5.00 kg baby
Replies
2
Views
2K
Introductory Physics - Finding "little g"
Replies
5
Views
3K
Where between the Moon and the Earth is the gravitational potential=0 ?
Replies
21
Views
3K
Gravitational potential for various matter configurations
Replies
1
Views
1K

Hot Threads

Recent Insights

Back
Top