Nov. 30- Dec. 4

Tuesday was the kinematics test, and on Monday we did a scavenger hunt review thing. Then, on Wednesday, we started the new unit on dynamics. A person held a basketball out in one hand and a bowling ball in the other. The two forces acting upon each ball is the force of the earth (like gravity) and the force of the person's hand. We decided that if the two were equal, the object wouldn't move, and if they weren't equal, it would be moving. For example, if the for of the earth was greater than the force of the hand, then the ball would be getting lower, and if the force of the hand was greater, the ball would be getting higher.

Then we started using force diagrams to model things instead of always having to draw pictures. In the diagram, the object the force was being exerted upon is represented by a dot, and the dot is labeled for what it is. We had arrows coming off of them from the top and bottom and side to side to represent force. Those were labeled for what the force came from and how much force in Newtons it was. The arrows opposite each other have opposite signs, so one arrow would say -__N while the other said +__N. Arrows could be stacked if there are two different forces, such as two people holding something. A number sentence for force would look like __N+__N=__N. If the total force is equal to zero, then the object isn't moving. Other objects could also be pushing and object. For example, a table would be pushing up on the ball while the earth is pushing it down.

We learned this stuff by holding bowling balls and pushing cars. This is useful because now we can figure out how much the push up or down or left or right on an object to get it to move a certain way.