What if the Earth Stopped Spinning Instantly?

You would be flung from wherever you are now at about 1,000 miles per hour and die.

The Earth spins at about 1,000 miles per hour (at the equator). When vehicles come to a sudden stop, like slamming on the brakes, their contents continue traveling at the original speed. If the Earth's spin came to a sudden stop, all people and objects not securely connected to the surface would continue traveling at 1,000 miles per hour. Houses would rip from foundations, and people outside would shoot through the air and skid across the ground. People inside would immediately slam into their walls and die, and people who had a lucky firm-grasp on a sturdy object would be ripped from their arms by the shoulders.

No one would fly into space, however.

To leave Earth's gravity, a person has to travel at least 25,000 miles per hour. 1,000 miles per hour is already accounted for, but a person would need an extra, 24,000 mile per hour boost to make it into space. So, there would be no death by cold, suffocating, or the vacuum of space.

Instead, people outside would fly several hundred feet through the air, only to accelerate rapidly back down to their doom. Depending on the angle, some people would be like skipping stones on a lake.

The awful part is that you would be fully conscious until impact. People who accelerate rapidly experience increased G-Forces and usually pass-out at a certain threshold. But because you are already traveling at 1,000 miles per hour, there is no "acceleration" and thus no merciful blackout period... just splat.

What if the Earth Stopped Spinning Slowly?

The people would all flock to the edge of night and day, and there would be war and famine.

If Earth stopped spinning at a slow and steady rate, such that nobody could feel the change, then we would all survive, but life would become very hard for everyone.

Night and day as we know it would be gone. One "day" would equal one "year." The Sun would scorch the surface of the Earth and the night would become bitter cold. In order for civilizations to survive, they would have to be capable of moving entire cities on a daily basis, and constantly travel the portion of the Earth between night and day where temperatures are livable.

Agriculture as we know it would cease, and permanent government territories would mean nothing. Conflict between nations would be inevitable, and if you're lucky or wealthy enough to survive, then your children will grow up with completely different views of life, seasons, and probably even of religion.