# Another old exam problem

1. Dec 13, 2003

### purduegrad

well doin lots of problems for finals and posting the ones i cant get...again im havin trouble with this reflection stuff

A solar sail of area A=200m^2 is at a distance 1.46e8 km from the sun. suppose the power of the sun is 10^20 kw and the sail is perfectly reflecting ( think you use f=2IA /c ) mass is 10kg, calculate the accel of the sail at this point in space...

again not sure here... how you get it

Last edited: Dec 13, 2003
2. Dec 13, 2003

### HallsofIvy

Staff Emeritus
Well, I don't know how you get D, because you didn't say what D means!
I would be inclined to think that D means "Distance" but you are explicitely told what that is.

The reason the answer is "real tiny" is that the power 1020 is divided by the surface area of a sphere with radius 1.45x1014km. before be multiplied by the area of the sail to get the power actually delivered to the sail.

3. Dec 14, 2003

### purduegrad

i dunno, im confused, lol we just need accel, i was gonna use newtons f=ma

4. Dec 15, 2003

### Staff: Mentor

Didn't you post a question about the pressure due to reflected light just a few days ago? Several folks answered, but you never responded. The same reasoning would apply here.

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