"Astronauts first feel the effect of weightlessness when the rocket engines are turned off. Straight away, they begin to float, held down only by seatbelts. Weightlessness allows astronauts to appear superstrong. They can lift objects that would be far too heavy to move on Earth. But there are some drawbacks.
Without the effect of gravity, blood and other body fluids begin to flow towards the head. This can cause a feeling of stuffiness and headaches. With no gravity to push against, bones and muscles can become weak. To stay fit, they have to exercise several hours each day. This allows them to recover more quickly when they return to Earth."
https://www.esa.int/kids/en/learn/Life_in_Space/Living_in_space/Gravity_and_weightlessness
"The sensation of weightlessness, or zero gravity, happens when the effects of gravity are not felt. Technically speaking, gravity does exist everywhere in the universe because it is defined as the force that attracts two bodies to each other. But astronauts in space usually do not feel its effects."
https://www.space.com/23017-weightlessness.html
"The speed of gravity on Earth is about 9.8 meters per second. We measure this by calculating the acceleration given to freely falling objects."
https://wiredcosmos.com/what-is-the-speed-of-gravity/