Examcracker Physics Question

[Rexhina]

Hi guys, i am stuck at this question and can't figure out the solution of how the answer was calculated.

ok so here it is:

The earth has a radius of approximately 6400 km. If an object could orbit the earth just at its surface, how fast would it have to travel?

the answer is 8 km/s but i dont know how come is 8 and not 80 km/s
when using the formula a=g=v^2/r

please help

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[Pisiform]

a = v^2/r

10 = v^2 / (6400*1000)

v = 8000m/s = 8km/s (u divide by 1000 to convert to km/s)

 

[Rexhina]

a = v^2/r

10 = v^2 / (6400*1000)

v = 8000m/s = 8km/s (u divide by 1000 to convert to km/s)

lol thank you, i must have had a brainfart because i kept getting 80