Question

The moon's period of revolution around the Earth is 27.3 d. How far away is the moon?
Question 5 options:
A) 1.33× 107 m/s
B) 3.83 × 108 m/s
C) 3.77 × 108 m/s
D) 4.88 × 109 m/s

Answer 1

by applying kepler's law of planetary motion , you can find the answer. its easy

Answer 2

How do you do that?

Answer 3

@CarlosGP

Answer 4

@daenio, something is wrong with the question as it is asking the distance however all the options are velocities. And I see 4 options, not 5 as announced

Answer 5

Velocity = (2 pi R)/T
T is the period and you are trying to find R

Answer 6

You can plug that for the velocity into:
F = G (Mm)/R^2 = mv^2/R

Answer 7

Why are all of your answers in: m/s
That is a velocity rather than a distance.

Answer 8

@CarlosGP Yeah, you're right. I totally forgot to change it. I notified my teacher earlier about the error.

Answer 9

@CarlosGP LOL, the question number is 5, not 5 options. Question 5.

Answer 10

Okay, I got B) for the answer!

Answer 11

@daenio, have a look at this

Answer 12

in VM should say RE and not RT

Answer 13

I think you're right. Not sure though. Anyways, as it turns out, C) is actually the answer.

Answer 14

Answer would be B) if you consider distance from the center of the Earth. C) is the answer if you consider distance from the level of sea, that is B) minus Earth's ratius=3.83x10^8-0.0637x10^8=3.77x10^8

Answer 15

Then B) or C) may be valid depending on where you are measuring from. I would take B) as it is usual to measure distance from center to center