Kepler's Third Law and Newton's Law of Universal Gravitation for Planet P

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Homework Help Overview

The discussion revolves around the application of Kepler's Third Law and Newton's Law of Universal Gravitation in the context of a hypothetical planet "P." The original poster presents a series of questions regarding the gravitational force exerted by the Sun on the planet, its orbital velocity, and the period of its orbit, while providing some initial calculations and equations.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to calculate the gravitational force using the formula for gravitational force and questions the accuracy of their results. They also inquire about the correct formula for orbital velocity and the period of the planet's orbit.
  • Some participants question the values used for Earth's mass and radius, suggesting corrections and emphasizing the need for accurate data in calculations.
  • Another participant raises a separate problem regarding the conditions for a driver to feel weightless in a car, discussing the relationship between gravitational force and centripetal force.

Discussion Status

The discussion is ongoing, with participants providing corrections to the original poster's numerical values and calculations. There is an acknowledgment of the original poster's edits, indicating some progress in their understanding. However, explicit consensus on the solutions has not been reached, and further clarification is sought regarding the weightlessness scenario.

Contextual Notes

Participants are working under the constraints of homework rules, which may limit the information they can provide or the methods they can suggest. There is a focus on ensuring that the original poster has the correct values for calculations, as inaccuracies have been highlighted in the discussion.

3dsmax

Homework Statement


a. Planet "P" has a mass that is 2.89 times that of the Earth, an equatorial radius that is 1.89 times that of the Earth and is located 7.8 times further from the Sun than the Earth is. What is the amount of force applied to the planet by the Sun?

b.what is the orbital velocity of planet "p". What formula do i use for that?

c.What is the period velocity of Planet "P"?

Homework Equations


a. Fg=6.67 e-11 (m1m2)/r^2

c. T^2=r^3

The Attempt at a Solution



NOTE THE EDIT: Fg= 6.67 e-11 [(1.99e30 x (2.89)(5.28e24)] / [(7.8)(1.5 e11)]^2

Fg= 1.48 e21
(but i know the answer is 1.68 e 21)
What did i do wrongFIXED THIS ONEc. t^2 = 7.8^3
t= 21.8 years
 
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5.28e24 is not the mass of the earth.
5.98324 first of all is not the radius of the earth, and second is not nearly the right magnitude. But anyway, what you want for this is the mean radius of Earth's orbit, since it says the planet is 7.8 times further from the sun than the Earth is.
I think you just need to get your numbers straight, then try it again.
 
okay well i fixed my numbers but and still getting the wrong answer
 
Never mind, I see your edit.
 
According to my sources, the mass of the Earth is 5.98x10^24 kg, not 5.28x10^24 kg. That is where the difference is.
 
well i figure it all out the only other problem that i am having now is on this:

1. A 55.0 kg person drives a 2300 kg car and cruises over the top of a hill with an 84.0 meter radius. With what minimum velocity can the car move so that the drive will feel weightless?

I used the formula mu = v^2/r/g
i figure since there has to be no normal to feel weightless so i figured there has to be no friction too. So set it equal to like 0. So then i did like v^2/84m/9.81. Can i do that or is there another way?
 
I don't understand the "mu". For the driver to feel weightless, the force of gravity must equal the centripetal force. So you can set them equal and solve for v.
 

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