A common schoolchild question is, "how come we don't feel the earth rotating?" The answer of course is that the earth moves at a constant speed.
Allow me to quote Earthsky.org:
Earth spins on its axis once in every 24-hour day. At Earth’s equator, the speed of Earth’s spin is about 1,000 miles per hour (1,600 kph). The day-night has carried you around in a grand circle under the stars every day of your life, and yet you don’t feel Earth spinning. Why not? It’s because you and everything else – including Earth’s oceans and atmosphere – are spinning along with the Earth at the same constant speed.
It’s only if Earth stopped spinning, suddenly, that we’d feel it. Then it would be a feeling similar to riding along in a fast car, and having someone slam on the brakes!
Think about riding in a car or flying in a plane. As long as the ride is going smoothly, you can almost convince yourself you’re not moving. A jumbo jet flies at about 500 miles per hour (about 800 km per hour), or about half as fast as the Earth spins at its equator. But, while you’re riding on that jet, if you close your eyes, you don’t feel like you’re moving at all. And when the flight attendant comes by and pours coffee into your cup, the coffee doesn’t fly to the back of the plane. That’s because the coffee, the cup and you are all moving at the same rate as the plane.
Now think about what would happen if the car or plane wasn’t moving at a constant rate, but instead speeding up and slowing down. Then, when the flight attendant poured your coffee … look out!
Sounds simple enough, right? It's NOT!
The reason you don't feel the difference between driving at a constant 65mph in your car, and cruising at a constant 500 mph in an airplane is that your velocity is linear in both examples.
Velocity is a vector (has a magnitude and orientation (direction) component), whereas speed is a scalar quantity. But under linear travel -- ie. moving in a straight line -- velocity and speed mimic each other from the human perspective. Thus, a constant speed or a constant, linear velocity is the same thing to us, and we don't feel it.
We humans, though, feel acceleration. But acceleration isn't just a linear component -- ie. from 0 to 60mph on a dragstrip; it also has an orientation component. Even if you move at constant velocity, but your orientation changes, that, folks, according to Isaac Newton is ACCELERATION. WE FEEL ACCELERATION!!
The Earth is Accelerating...We Feel Acceleration!
Just because the Earth supposedly moves at constant speed does not mean we are not accelerating. If we are spinning on our axis, then our orientation is constantly changing.
Check out my diagram below
We literally move 360 degrees at 1,600 kilometers per hour at the equator! Combined with the fact that we're hurtling through space, orbiting the sun at some unimaginable velocity, that sounds like serious G-forces!
Imagine going to an empty parking lot and doing donuts in your car at a constant 30mph...are you telling me that you're not going to feel the constant orientation change of your car? Give me a break!
Now imagine spinning at 1,600 km/ph...north, west, south, east, north, west, south, east...you get the idea!