# Tough physics problems

mobius
The Earth orbits the Sun once a year at a distance of 1.50x1011 m. Jupiter orbits the Sun at distance of 7.78 x 1011 m. These distances are between the centre of the planet and the sun. How long ( in Earth days ) does it take for Jupiter to make one orbit around the Sun?

T(period = 8.64E4 sec) = 2&pi;r^(3/2)/&radic;(GMearth)

i have tried adding and subtracting the two radiis together and then plugging it into the equation...however it is incorrect....i am either not understanding the problem or is it just human error....?

Last edited:

Staff Emeritus
Gold Member
Hi mobius,

We welcome homework problems here, in the Homework Help forum. We also ask that you attempt the problems first, and show us your work up to the point where you get stuck.

- Warren

Mentor
Originally posted by mobius
i cannot manipulate the formula in order to solve this, maybe it's because i do not understand the problem fully...i just need an explanation on setting this up....much appreciated

Start by identifying all the forces acting on the body (the pilot), then tell us what you know about acceleration, circular motion, and Newton's laws!

rohitr30
Hint: You use keplers third law where (time period)^2= (radius of orbit)^3

bsrishu
if I'm not understanding wrong, we have to find the 'relative' time period of the planet w.r.t earth. Here relative means : let car A & B start from pt. P in diff. Circles with diff. Speeds. Now relative time period will be that when both will reach pt. Again simultans. To do this problem u can take the help of concept of beats from waves.
Therefore use this:
1/T=1/T1 - 1/T2
Where T1 , T2 are the periods of Earth and Jupiter resp.
Tell me if it's right