Physics 101

The earth spins ~1000mph

No. Rate of spin is measured in revolutions per unit time. The Earth rotates at 1/60 x 24. = 1/1440 rpm, or 1/24 revs per hour.

But as it's Boxing Day, what the hell:

- The radius of the Earth is ~4000miles, so its circumference, say at the equator is 2 x π x 4000 which comes to ~25,000miles.

- The tangential speed at the equator is therefore 25000miles/day, which is close to 1000mph, I agree.

- The centripetal acceleration needed to keep an object moving with tangential velocity v, in a circle of radius r, is

**v²/r**. (Physics 101). So, for an object at the equator, the apparent centrifugal acceleration it experiences, counter to the acceleration of gravity, will be 1,000,000/4000 =

**250 miles/hr². **
What we need to know is how this acceleration compares with g, the acceleration due to gravity, which is about 10m/sec². To do that, we need to get this result into the same units as g is quoted in:-

1 mile is ~1600m. And 1hr is 3600 seconds. So 250 miles/hr² becomes 250 x 1600/(3600)² = 25 x 16/(360 x 36) = 25 x 4/(360 x 9) = 100/3240 =

** ~ 0.03 m/sec². **
So the centrifugal force at the equator, as a proportion of the force of gravity, is of the order of 0.03/10 =0.003, or

** 0.3%.**
In other words, it is nowhere near strong enough to cause water or anything else to be flung off.

P.S. To check my arithmetic, I went to the people who faked the moon landings

....and got a similar figure. Details here:

https://www-spof.gsfc.nasa.gov/stargaze/Srotfram1.htm
So either you have to agree they are right, or you have to dispute F = mv²/r, i.e. Physics 101. Have fun!