Newton's First Law

I had jury duty today, so your assignment was to read and take notes on sections 4.4 and 4.5 in the blue book OR sections 3.4 and 3.5 in the brown book. These have exactly the same information; they are just different editions.

These sections talk about Newton's First Law and the difference between mass and weight.

The Wikipedia article on Newton's First Law is actually pretty good, which you can find here. The Law basically says that without a net force acting on it, an object will just keep doing whatever it was doing. If it was at rest, it'll stay at rest. If it was already moving, it will keep moving in a straight line.

Here is a nice tidbit on the difference between mass and weight. On Earth, an object weighs 9.8 Newtons for every kilogram of mass it has. For example, I have a mass of about 60 kilograms, so on Earth I weigh about 588 Newtons (~133 pounds). On the moon, where the gravity as about one sixth as strong, I would still have a mass of 60 kilograms, but I would weigh only 98 Newtons (~22 pounds).

Homework tonight is "Force and Newton's First Law." We will go over some of the problems when I get back tomorrow, and it is due tomorrow.