# gravitational field

### Happy g day

Actually, it should be called Happy "Magnitude of the local Earth gravitational field" day. You know, 9.8 N/kg on September 8 (9/8). Get it? Well, the idea was for the physics students and faculty to build some stuff to do outside - projectile motion type stuff. Well, we had the idea a while ago and then kind of forgot about it. In order to just get something done, I set up the "shoot the falling target" demo. (previously known as shoot the monkey). Here is a quick video demo (seriously - first take too). What is going on here and what does this have to do with g? Well, it doesn't…

### Basics: The electric field

Suppose I take a 1 kg ball and hold it near the surface of the Earth. What would be the gravitational force the Earth exerts on this ball? And I could say "g" is: The magnitude of this force would then be 9.8 Newtons. And, if I replaced the ball with a 10 kg ball, the force would be 98 Newtons. What does this have to do with the electric field? Well, you are probably already familiar with this idea of the gravitational force. Guess what? "g" is the gravitational field. Basically, it is the force per unit mass due to the Earth. This is only approximately constant. If I get very far…