Gravitational Potential Energy question

AI Thread Summary
The discussion revolves around calculating the gravitational potential energy (GPE) of two planets, PICA-9 and PICA-10, orbiting the star PIC-2A, which has the same mass as the Sun. The user has determined the orbital distances and velocities but is unsure how to proceed with the GPE calculation without the planets' masses. The appropriate formula for GPE is confirmed to be PE = -GMm/r, while the mgh formula is deemed unsuitable for this context. It is noted that the masses of the planets are essential for calculating GPE, but the information provided does not allow for their determination. The conversation highlights the challenge of incomplete information in physics problems.
stefiex
Messages
2
Reaction score
0
Hello! I'm having some problems with a question that my professor has given me. Below is the question. I have already figured out the planet's orbital and angular-orbital velocities, but included that part due to the fact that some information was included.
PICA-9 and PIC-10 are planets orbiting its star, PIC-2A. Find each of the planet's orbital and
angular-orbital velocity if PIC-2A has the same mass as our Sun, PICA-9 is 1.0 A.U. away from
the star and PICA-10 is 5.5 times further than PICA-9. What are the gravitational potential
energies of each planet with respect to the star?


Homework Equations


Since everything must be in m/kg form, I have figured out that:
Distance from PICA-9 and PICA-2A is 1.50X1011m
Distance from PICA-10 and PICA-2A is 8.22X1011m
PICA-2A mass is 1.989X1030kg
G=6.67X10-11


The Attempt at a Solution


Since the formula for GPE given to me is -GMm/r (G=gravity in space, M="the anchor" mass, m=orbiting object's mass, and r=the distance between the planets), I wasn't sure if PE=mgh would be a helpful formula in this case. Would finding the kinetic energy be helpful as well? How would I find the mass of the planets?
Thanks for reading!
 
Physics news on Phys.org
Hello stefiex and welcome to PF!

Stick with PE = -GMm/r. PE = mgh is only an approximation that is valid when m is near the surface of a planet or star.

Unfortunately, you will not be able to calculate PE without knowing the masses of the planets and there is no way to deduce those masses from the information given.
 
That's what I thought. My teacher is notorious for forgetting information needed to complete the problem. Thanks for taking the time to look at it!
 

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 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
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

Gravitational potential energy traveling from earth to mars
Replies
7
Views
3K
Variation of escape velocity with equal surface gravity
Replies
7
Views
1K
Misunderstanding of Gravitational Potential Energy
Replies
7
Views
3K
Gravitational Potential Energy questions near the surface of a planet
Replies
8
Views
2K
Conservation of Energy with Gravitational Potential Energy
Replies
6
Views
2K
Gravitational equipotential multiple choice problem
Replies
4
Views
2K
Gravitational Potential Energy
Replies
2
Views
1K
Potential Energy and raising a satellite from Earth into a Circular Orbit
Replies
5
Views
2K
Question about gravitational potential energy and angular motion
Replies
4
Views
1K
Velocity of two masses due to electric potential energy
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top