## Compassionate 2 years ago Let's see how smart OpenStudy is. The light from the sun travels 187,000mps It hits earth in 8min. How far away is the earth form the sun given this information? How long would it take a Sakura Blossom falling at 5cm/sec to reach Earth from the Sun? Find the force being exerted by the light upon the Earth and how far the earth moves each year by the implications of light imposed upon Earth. Given the earth weighs: 5.972E24 kg How smart is OpenStudy? Lets see.

1. AravindG

$Speed=\dfrac{distance}{time}$

2. AravindG

$\LARGE \text{speed of light} =3 \times 10^8$ approx

3. AravindG

so I guess you can do part 1

4. Compassionate

>How long would it take a Sakura Blossom falling at 5cm/sec to reach Earth from the Sun?

5. AravindG

in part 2 you are given the speed and distance ,find time

6. AravindG

distance is got from part 1 :)

7. Compassionate

Correct. But you're not given the time at 5cm/s

8. AravindG

Part 2 asks for the time !!

9. Compassionate

There is no part 1 and 2. This is all one.

10. Compassionate

You want to find the distance given the speed and time.

11. ParthKohli

$\rm force = mass \times acceleration$

12. PeterPan

Let's see how smart OpenStudy is. --Part 1-- The light from the sun travels 187,000mps It hits earth in 8min. How far away is the earth form the sun given this information? --END Part 1-- --Part 2-- How long would it take a Sakura Blossom falling at 5cm/sec to reach Earth from the Sun? --End Part 2-- Find the force being exerted by the light upon the Earth and how far the earth moves each year by the implications of light imposed upon Earth. Given the earth weighs: 5.972E24 kg I'm sure this was what Aravind meant when he said part 1 and part 2

13. ParthKohli

Since the mass of light is $$0$$, we can just say that light exerts a force of $$0N$$? I don't know, I am not so good at Physics. I think light does exert some force.

14. AravindG

@PeterPan thanks .Its always a good idea to break a question into parts :)

15. Compassionate

In fact, light does move the earth every year. I am asking you to find out given little information.

16. Compassionate

True, light has no stationary mass, but it has a force. Light can burn things, and that's a form of force.

17. AravindG

Light (as in photons) carries momentum. Any change in that momentum (such as absorption or reflection), will impart a force. So yes, it can exert a force. @ParthKohli

18. Compassionate

So, the question stands, how much force is exerted upon the earth each year and as a result moves it back.

19. AravindG

maybe @JamesJ can enlighten us on this

20. AravindG

what I can only predict is that the force may be around 1 newton or less,

21. AravindG

@Compassionate do you have the answer with you ?

22. Compassionate

I do.

23. JamesJ

Sure, the sun does exert a radiation pressure on the earth of around 4 microPascals, nearly all of it absorbed. So the force isn't quite as low as 1 Newton, but the acceleration due to it is tiny.

24. AravindG

I think he needs a numerical answer James

25. JamesJ

I'm not going to do the calculations here myself. I'll ask the questioner what they know about radiation pressure, and what relations they have that can help. I'm happy to be a thought partner. But not right now; I'm going to bed.