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Physics

Calculate the orbital time period in years for a planet going round the Sun in an orbit of radius twice that of Earth. Give your answer to 3 significant figures.
You may use Kepler’s Third Law for this question. T^2 = (4π^2/GM)r^3
You then substitute the mass of the Sun and the diameter of the Earth into the equation to find T, the period.
Reply 2
For objects orbiting the sun there are some very handy natural units.

Orbital radius - AU (1 AU is the average sun earth distance)

Orbital period - Year (time for earth to orbit the sun)
Mass = mass of the sun

Then Kepler 3 is just T^2/ R^3 = 1

And if you do your working out this way the answer will pop out in units of earth year without any further conversion.

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