Question

For a satellite to stay in orbit around Earth, it has to be moving forward very fast all the time. What force will make it fall to Earth if it goes too slowly?

Earth's gravity

the force of friction

the magnetic force from Earth's north pole

the Sun's gravity

Answer 1

Most important
Centripetal force which makes it attract towards the earth and makes it able to move around

Answer 2

Maintaining an orbit has nothing to do with the satellite's speed.
ANY (tangential) speed is enough to stay in orbit, if the satellite
just stays away from Earth's atmosphere.

If the satellite completely stops moving 'sideways' at all, and just
hangs there, then the forces of gravity between the satellite and
the Earth will pull them together ... the satellite will fall into the
atmosphere and then to the ground.