Conceptual Physics

1
Conceptual Physics Study Notes Questions
Forces (Chap. 4)

1. A force is a push or pull. It can seem to be
   delivered by a solid or fluid, but ultimately it
   is conveyed by force fieldssuch as attraction or
   repulsion from an electromagnetic field (e.g.
   around atoms, pushing against one another), or
   gravitys pull.
2. Isaac Newton (1665) described how we observe
   forces acting in our everyday lives with his 3
   Laws of Motion.
3. Describe the 1st Lawthe Law of Inertia (p81).
   The measure of inertia is mass, but what is
   inertia? Is the inertia of a stationary object
   the same when the object is moving?
4. Describe the 2nd Lawthe Force Law (p84). Does
   the presence of a force necessarily mean that
   something is accelerating? Is force a vector or
   scalar? What happens when the sum of external
   forces acting on an object equasl zero? Does this
   mean nothing is happening (think about a SCUBA
   diver deep underwater)? Distinguish balanced vs
   unbalanced forces (p82).
5. Describe the 3rd Lawthe Law of Reaction Force
   (p87). How does a rocket work? Does a rocket work
   without air from which to push off?
6. A closed frame of reference is one in which all
   forces acting are internal (that is, a frame
   wherein the only interactions that occur are
   between the objects within that frame). Such a
   thing is never really possible (gravity is always
   present), but within the considerations of a
   particular problem, some reference frames can be
   considered enclosed.
7. Consider the horse and buggy problem on page 88.
   What is the proper closed frame of reference to
   reconcile the seeming contradiction of the 2nd
   and 3rd Laws (Hint think big). How would this
   problem change if the horse wear roller skates?
8. What is the MKS unit of force? What is the
   English system unit of force? Is weight a measure
   of force or mass?