The Student Room Group

Physics Synoptic Paper Question

This question is taken from Edexcel Salters Horners Physics Synoptic Paper Friday 20 June 2003. I have no idea how to answer this question. I don't want the answer, but can someone point me in the right direction? Bear in mind the information in the question is the only information given - nothing like the mass of the earth or sun, or distance from the earth to the sun is given.

Question:

Cosmologists have found evidence for a planet orbiting a distance star called Tau Bootes. This star is about the same mass as our sun. The spectrum of light from this star varies with time. Initial results suggested that the spectrum included a small amount of reflected light coming from the surface of the orbiting plane
The light reflected from the planet surface is
- blue-green
- periodically getting brighter, then dimmer
- of varying wavelength, due to the planet's orbital speed

The final observation led to the deduction that the orbital speed is about 70km s^-1

Deduce whether this planet is closer to or further from its star than the Earth is from the Sun and discuss these three obsdervations. (the Earth has an orbital speed of abou 30kms^-1 )
Reply 1
the star has the same mass as the sun, so has the same gravitational potential distribution. the planet has a higher kinetic energy (because it has a higher orbital speed), and so it must have less GPE, and so it must be closer to the sun than the earth
Reply 2
Are those what synoptic questions are like? that's pretty interesting, im gonna have a look at some more.
Reply 3
elpaw
the star has the same mass as the sun, so has the same gravitational potential distribution. the planet has a higher kinetic energy (because it has a higher orbital speed), and so it must have less GPE, and so it must be closer to the sun than the earth


ah ha! belive it or not that makes a lot of sense. Thanks :-)