A) Radiation from the Sun reaching Earth (just outside the atmosphere) has an in

Question

A) Radiation from the Sun reaching Earth (just outside the atmosphere) has an intensity of 1400 W/m2. What would the intensity be at Pluto? (See Appendix B, A-3)?

B) /H earth)/(distance to planet)
Assuming that Earth (and its atmosphere) behaves like a flat disk perpendicular to the Sun's rays and that all the incident energy is absorbed, calculate the force on Earth due to radiation pressure.?

C) What would it be for Pluto?

D) What is the force on the Earth due to the sun's gravitational attraction?

E) What is it for Pluto?

Explanation / Answer

Solution:

Here;

Intensity I = 1400W/m2

and as we know;

Surface area of earth = R2

& R = 6400 km = 6400000 m

c = 3*108 m/s (Speed of light)

we know that radiation pressure if all the incident energy isabsorbed is P = I/c

=> P = 1400 W/m2/ 3*108 m/s

=> 466.67*10-8 N/m2  

Hence, due to this radiation = P*A

=>(466.67*10-8 N/m2)**(6400000 m)2

=> 6*108N

and

The Gravitational force due to the Sun is Fg =GMm/r2

Here,G =6.67*10-11Nm2/kg2

M = mass of sun = 2*1030 kg

m = mass of earth = 6*1024kg

r = distance between the sun and earth =1.5*1011m

=> Fg = 6.67*10-11*2*1030*6*1024/(1.5*1011)2

=> 35.57*1021N

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