PHYSICS CHAPTER 4 NOTES
VECTOR ANALYSIS
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Force--that which produces or prevents motion or has a tendency to do so. A force is a vector meaning it has both
magnitude and a direction.
Forces
a.
Never act alone (they occur in pairs in opposite directions)
b.
Can produce motion
c.
Can be exerted through long distances (gravitational force)
Resolution of forces-- (Vector Analysis new term) a procedure of finding component forces. A separation into
components (x, y, z) that will produce the same effect.
Normal Force--is a force that is perpendicular to the surface in question.
Concurrent Forces--two or more forces having lines of action that pass through the same point.
Resultant Force--is a single force that produces the same effect as several forces acting concurrently.
a.
The resultant of two or more forces that produce the same effect as several forces acting concurrently.
b.
The resultant force vector of two forces acting at an angle upon a given point is equal to the diagonal of a
parallelogram of which the two force vectors are sides.
Vector Analysis--is a mathematical procedure in which two or more vectors in 1 or more dimensions can be combined to
produce a single resultant vector.
Equilibrium--is the state of a body in which there is no change in its motion.
a.
The First Condition of Equilibrium-- (translational equilibrium) there are no unbalanced (net) forces acting on a
body.
b.
The Second Condition of Equilibrium-- (rotational equilibrium) in a given plane the sum of all the clockwise
torque's is equal to the sum of all the counterclockwise torque's about a given point.
Equilibrant Force--is equal in magnitude to the resultant of two or more concurrent forces and acts in the opposite
direction. The equilibrant force if applied to a system would restore equilibrium.
Friction--is a force that resists motion of objects that are in contact with each other.
a.
Friction acts parallel to the surfaces that are in contact and in the direction opposite to the motion.
b.
Friction is dependent upon the nature of the frictional materials in contact and the smoothness of their surfaces.
THE Y-COMPONENT OF THE WEIGHT IS CONSIDERED WHEN CALCULATING THE FORCE
OF FRICTION.
c.
Static Friction--is the frictional force between stationary objects.
d.
Kinetic Friction--is the frictional force between objects that are sliding with respect to one another. Usually has
a smaller coefficient than static friction.
e.
Coefficient of Friction--ration of the force of friction to the normal (perpendicular) force pressing the surfaces
together. The Greek letter mu represents the coefficient.
Parallel Forces--are forces that act in the same or in opposite directions at different points on an object. The resultant of
these parallel forces is taken from the center of mass.
Center of Mass-- (center of gravity) of any object is that point at which all of its weight can be considered to be
concentrated.
Moment Arm-- (torque arm) a perpendicular line drawn from the pivot point to the vector. Distance along this moment
arm is used in calculations to find torque.
Pivot Point—(fulcrum)--a stationary point in which objects rotate.
Torque--are the product of a force and the length of its moment arm. The unit of the torque is the Newton meter (N-m).
T = Fd
Couple--two forces of equal magnitude act in opposite direction in the same plane, but not alone the same line.