2. » In nature, there are two general types of forces: » » 1. Fundamental forces » 2. Non-fundamental forces

3. » 1. Fundamental forces: those that are truly unique in the sense that all other forces can be explained in terms of them. Only three have been discovered: » Gravitational force » Strong Nuclear force: stabilizes the atomic nuclei » Electroweak force: has two manifestations: ˃i) electromagnetic force which charged particles exert on one another ˃ii) weak nuclear force which influences radioactive disintegration of some nuclei

4. » 2. Non-Fundamental forces: are actually subsets of the fundamental forces. For instance, friction and tension forces are related to the electromagnetic force which arises from the interactions between electrically charged particles comprising atoms and molecules.

5. » We've all been pretty darn accepting of the fact that we use 9.8 m/s 2 for the gravitational acceleration on Earth. » But why is that? What causes gravitational acceleration?

10. » Definition of Weight » The weight of an object on or above the earth is the gravitational force that the Earth exerts on the object. The weight always acts downward, toward the center of the Earth. » On or above any other astronomical body, the weight is the gravitational force exerted on the object by that body. »

11. » *Notice that the farther one is from the center of the Earth, the less the Weight... » on top of Everest? Less Weight. » Out in space? Less Weight.

13. » **Note that the Law of Gravitation as written applies to particles as opposed to bigger objects, but it works very well as a close approximation for things like the Earth in which the mass of the object is symmetrically distributed about its center. » When the mass is not evenly distributed about the center, we need calculus to come up with a more precise answer - the calculus students will learn how to do this type of thing around February or March of this year! :)

16. »If the Lunar Module weighs 6 times MORE on earth than it does on the moon, but we want to have the same horizontal acceleration of the vehicle, is the required force on the moon: »(a) the same, »(b) greater than, or »(c) less than, the force on the earth? WHY?

17. »P. 128 #20, 21, 24-25, 27-28, 30, 33