## Moon's Velocity

### How fast is the Moon moving around the Earth?

1 – What do we need to know?  We need to know the total length of the Moon’s path as it orbits the Earth.  We also need to know the time that it takes to make one complete orbit.  Speed is stated as a distance over time.  Like “miles per hour” or “feet per second”.

2 – To calculate the Circumference of the Moon’s orbit we will use our formula

Circumference of a circle:  C = 2piR

We know what pi = 3.14 and we know what 2 equals, so let’s find out what R (Radius) equals. The Radius of the Moon's orbit is the sum of the radius of the Earth (A = 4,000 miles) and how far the Moon is from the Earth (B = 240,000 miles).

So the Radius (A + B) equals 244,000 miles.

The Circumference of the Moon's orbit is C = 2piR = 3.14 x 244,000 miles = 1,532,320 miles.

We're going to round off that number so  C = 1,500,000 miles

It takes the Moon 29.5 days to go from full moon to full moon (a complete orbit).  Since we usually think of speed (or velocity) in terms of "miles per hour" or "kilometers per hour", we will need to find out how many hours there are in 29.5 days.

29.5 days x 24 hours per day = 708 hours

We know the distance (1,500,000 miles) and we know the time that it takes (708 hours).

If we divide the distance in miles by the time in hours, we come up with the "miles per hour" that the Moon is traveling around the Earth.

1,500,000 miles / 708 hours = 2,119 miles per hour.  We'll round this off to 2,100 miles per hour.

To summarize our calculations:  The Moon is traveling around the Earth at about 2,100 miles per hour.