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The Earth takes one year to orbit the Sun at a distance of 1.5 x 10^11 m. Calculate i

The Earth takes one year to orbit the Sun at a distance of 1.5 x 10^11 m. Calculate its speed.

Speed = distance/time

(1.5 x 10^8)/ (365*24*60*60) = 4.75646... kms-1

Why is the answer in the book 29.9 kms-1?

Reply 1

DumpOrStay?

Because your title has to the power 11 and your working has to the power 8, maybe?

Either work in metres or km.

Reply 2

didgeridoo12uk

distance is wrong. you've used the radius not circumference.

basically you've calculated what the average speed of the earth would be if it took a year to crash directley into the sun

(edited 13 years ago)

Reply 3

tieyourmotherdown

Like, really really fast.

Reply 4

Swoosh

Original post by DumpOrStay?

Because your title has to the power 11 and your working has to the power 8, maybe?

Either work in metres or km.

I changed the distance to km because the answer in the book is given in km. If I do the same sum with x10^11 it's just 1000 x bigger :confused:

Reply 5

Dynasty

i =

\sqrt -1

Reply 6

Swoosh

Original post by didgeridoo12uk

distance is wrong. you've used the radius not circumference.

basically you've calculated what the average speed of the earth would be if it took a year to crash directley into the sun

Ah ok.

So the distance given is the radius? So the correct sum would be

(2 x pi x 1.5x10^8) / (365*24*60*60)

= 29.8857...

Yay :smile:

Thanks

Reply 7

Steven

The motion is circular, so you must find the circumference of the orbit first.

Pi x diamter = 3.14 x (2x1.5x10^8)=9.24x10^8.

Then use speed = distance/time

Speed = 9.24x10^8) / (365x24x60x60)=29.885 kms^-1