How Much Force Does Sunlight Exert on Earth?

[machinarium]

Homework Statement

The intensity of radiation reaching the Earth from the sun is 1350 W/m2. The Earth's radius is 6.4 × 106 m. How big a force does this radiation exert on the Earth (Assume it is all absorbed)

The Attempt at a Solution

F=AP=AI/c=2.3x10₉ N

That's my answer. Is that correct?

(The result in my material is 5.8x10⁸ N)

And I want to ask one more question?
What is the difference between I or S_av and S in calculation?
If we say the Sun delivers about 10000 W/m² of energy to the Earth's surface, so that is S_av, right?

Then they told me to calculate the total power.

I see a book solved by telling P=S_avA and another book was P_av=S_avA.

Which one was correct? Or was P_av the same as P?
Then is this one P=SA.

 

[tiny-tim]

hi machinarium!

your answer is 4 times too much …

did you square the diameter? ​

the precise equation is instantaneous power = instantaneous intensity times area …

and therefore average power = average intensity times area …

in AC electric circuits the difference between instantaneous power and average instantaneous is quite important, and with lasers also, but I don't see how you could measure instantaneous power or intensity for an incoherent source like sunlight, so that has to be average (so there's not much point in saying so)