# Search results

1. ### Things spinning in circles

This is what i dont get for things spinning in circles. So let's say you tie a mass to the end of a string, and you start swinging the string around in a circle with a constant speed. In the absence of air resistance, then the net force on the mass would be the centripetal force provided by...
2. ### Does the force of gravity ever have a reaction force?

but if you can say the reaction force to gravity is gravity, how can you say the reaction force to friction is friction? so if you push the book lightly foward and it doesnt move, there must be a frictional force opposing the force of your hand. But your hand and the friction are not action...
3. ### Does the force of gravity ever have a reaction force?

for example, a book is at rest on a table. One might say that the normal force is the reaction force. BUt reaction forces always have to be equal in magnitude, and you put an object on the book, then the normal force would increase to keep the book at rest, therefore the normal force is...