# Homework Help: Earth colliding with sun problem

1. Sep 16, 2008

### Benzoate

1. The problem statement, all variables and given/known data

If the Earth were suddenly stopped in its orbit, how long would it take for it to collide with the sun?(Regard the sun as a fixed point mass. You may make use of the formula for the period of the Earth's orbit.

2. Relevant equations

tau=(4*pi^2*R^3/M*G)^.5

3. The attempt at a solution

Should I considered the velocity of the earth before it came to a halt in its orbit? ; the radius between the two bodies are obviously not fixed. What do they mean when they say regard the sun as a fixed point mass?

2. Sep 16, 2008

### mgb_phys

It says the earth stopped, so no.

It means just assume all the suns mass is at the centre, you don't have to worry about the mass near the edges of the sun pulling the earth at a slightly different angle.
It 'probably' also means you work out the time for the centres to collide, not the time for the edge of the earth to reach the outer edge of the sun.