# Q & A: Slowing Everything Down

Q:
Need to understand principles involved in Friction.
- David castillo (age 11)
El Paso, Tx
A:
Friction is a force that tends to make things next to each other move together or stay put together. If you take a book and push it across the table, as soon as you let it go it slows down and stops because of friction. Newton’s laws say that an object in motion tends to stay in motion unless acted on by a force. In the case of our book, this force is friction.

But where does friction come from? Even though the book and table appear to be smooth, if we could see the individual atoms (the smallest pieces of matter) that make up the book and the table, it would not really be smooth. In fact, it is very rough. So when the book slides over the table, the atoms are bumping into each other as they slide.

There are 2 things that affect how strong friction is. The first is called the coefficient of friction. That basically means how rough the surface the atoms move over is. The other important thing is the weight of the object. Heavier objects are much harder to push across the floor because their atoms get pushed harder into the very tiny gaps in between the atoms of the floor. That means there is more friction.