Question

Using the length of the day, compute the speed of a object on the earth's equator due to the earth's rotation (=6,370km)

Answer 1

The speed is distance over time. The distance is the length of the equator circle:

$$d=2\pi R,\\\space\\ v=\frac dt=\frac{2\pi R}{t},\\\space\\ v=\frac{2·3.14·6370}{24}=1668\text{ km/h}.$$