Class on 10/19/09

Today in class we discussed a couple of concepts.  The first concept we discussed was Newton's 2nd Law.  This law states that  a = Fnet/m.  This law is also stated as Fnet = ma.  In both of these cases m = mass and a = acceleration.  There are many ways to interpret this formula.  First of all, it is shown that mass is inversely proportional to to acceleration.  This can also be proved by showing that 1/a is proportional to m.  Also, in this formula is it shown that acceleration is directly proportional to Fnet.  All of these conclusion can be proved by breaking down the formula a = Fnet/m.

Examples:

1/a  (proportional to)  m    a  (proportional to)  Fnet  a  (proportional to)  1/m

The other concept we discussed was free - body diagrams.  We went over an exercise we completed in Minds on Physics, and discussed all possibilities with the problems given.  There were examples when we would be given a diagram, and we would have to say whether or not it was valid, and also examples when we would have to name forces given the description of an event and a valid diagram.  We then discussed free - body diagrams and what goes in them.

• They show forces that act on an object
• They only show forces (no velocity or acceleration vectors)
• They NEVER show Fnet
• All vectors start at a center point and move in the direction of the force in relation to the object
• All forces are resembled by vectors

In class, we also had time to work on our labs and have small discussion about the main ideas of the lab.  At the end we were given some time to work on homework, and put some finishing touches on our lab.