Measuring gravitational field on another plane with a pendulum

Click For Summary
SUMMARY

The discussion focuses on calculating the mass of a planet using a pendulum to measure gravitational acceleration. The astronaut uses the formula T = 2π * sqrt(L/g) to derive gravitational acceleration (g) and applies Newton's law of universal gravitation (g = GM/r²) to find the planet's mass. The final calculation yields a mass of approximately 1.17275 x 10²⁵ kg after correcting the radius squared in the equation. This demonstrates the application of classical mechanics in extraterrestrial environments.

PREREQUISITES
  • Understanding of pendulum motion and the formula T = 2π * sqrt(L/g)
  • Familiarity with Newton's law of universal gravitation (g = GM/r²)
  • Basic knowledge of units of measurement in physics (e.g., meters, kilograms)
  • Ability to perform algebraic manipulations and solve equations
NEXT STEPS
  • Study the derivation of the pendulum period formula and its applications in different gravitational fields
  • Learn about gravitational acceleration variations on different celestial bodies
  • Explore advanced applications of Newton's law of universal gravitation in astrophysics
  • Investigate the implications of mass calculations on planetary formation and dynamics
USEFUL FOR

Students in physics, astrophysics enthusiasts, and anyone interested in gravitational studies and celestial mechanics will benefit from this discussion.

chara76
Messages
10
Reaction score
0

Homework Statement



An astronaut arrives at a new planet, and gets out his simple device to determine the gravitational acceleration there. Prior to this arrival, he noted that the radius of the planet was 7040 km. If his 0.400-m-long pendulum has a period of 1.0 s, what is the mass of the planet?

Homework Equations



T = 2pi * sqrt(L/g)

The Attempt at a Solution



g = (4pi^2*(0.400))/1^2 = 15.79 m/2^2

I was given this equation as a hint, but I can't figure out where to go from here to get mass.
 
Physics news on Phys.org


Newton's law of universal gravitation (equation) should get you there. Combine that with Newton's second law of motion (a = F/m) and solve for the remaining m. :smile:
 
Last edited:


Ok, this is what I get:

g = (GM)/r^2 --> 15.59=[(6.674x10^-11)(M)]/7040000

M=1.6656 x 10^18 kg

Is this correct?
 


chara76 said:
Ok, this is what I get:

g = (GM)/r^2 --> 15.59=[(6.674x10^-11)(M)]/7040000

M=1.6656 x 10^18 kg

Is this correct?

I think you forgot to square the radius.
 


Thanks for catching that. How does this look?

g = (GM)/r^2 --> 15.59=[(6.674x10^-11)(M)] / (7040000)^2

M=1.17275 x 10^25 kg
 


Looks okay to me. :approve:
 

Similar threads

  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 23 ·
Replies
23
Views
5K
Replies
2
Views
3K
Replies
2
Views
2K
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
2
Views
2K