Register to reply

Force on Earth by the radiation pressure of Sun

by SL_1719
Tags: earth, force, pressure, radiation
Share this thread:
Jan31-11, 01:23 PM
P: 9
1. The problem statement, all variables and given/known data
Estimate the force on Earth due to the pressure of the radiation on Earth by the Sun. (At Earth's orbit, the intensity of sunlight is 1.37 kW/m^2.)

2. Relevant equations
Radiation Pressure=I/c
Using SA of earth=510,072,000 km2

3. The attempt at a solution
So I have been working at this problem for a while now and can't seem to get the correct answer. I found the radiation pressure to be 4.5667e-6 N/m^2. I have since then tried taking this and multiplying it by the surface area of the earth in many different forms to no avail. What am I missing? I have tried these coefficients to Prad*SA, 1 (acting on whole surface), 1/2 (half the surface since sun is on one side), 1/(2sqr2) (thought possibly rms), 1/sqr2 (similar to before, just trying anything), and 1/(4sqr2), 1/4. My force for Prad*SA=2.329e9 N.
Phys.Org News Partner Science news on
Pilot sites in energy from coffee waste show good results
Startups offer banking for smartphone users
Factor in naked mole rat's cells enhances protein integrity
Jan31-11, 01:54 PM
HW Helper
P: 3,394
Welcome to PF!
I agree with 4.5667e-6 N/m^2.
I'm puzzled with what area to use. The sun only shines on one side of the Earth at a time so you certainly wouldn't use the whole surface area. Half of it doesn't seem right either because the sun hits a good part of it at a very high angle, drastically reducing the intensity. I think taking the area to be πrē is the best first estimate because it counts all of the radiation hitting the Earth. Of course all this assumes that the radiation is absorbed rather than reflected.
Jan31-11, 02:38 PM
P: 9
Thank you for welcoming me and thank you for the help, using just pi*r^2 worked. 5.823e8 N is the answer.

Register to reply

Related Discussions
Gravitational Force Between; Sun and Earth, Moon and Earth Introductory Physics Homework 21
What radiation can be detected at 1km high from Earth surface? Astronomy & Astrophysics 1
Force of solar radiation on earth Introductory Physics Homework 4
Natural Gamma radiation from Earth Cosmology 0
Background radiation on Earth quantified? Nuclear Engineering 3