Announcement
Due to an accident, Prof. Kleinman will be unable to
Instructor: L. Frommhold, RLM 10.324; 471 5100 email: [email protected] office hours: MWF 1111:50 a.m. at RLM 10.324
teach this PHY302K course. I have been asked by the Chairman,
What is Force ?
Accordig to Webster, FORCE means many things:
strength or energy exerted or brought to bear cause of motion or change active power capacity to persuade or convince legal efficacy (. . . a law still in force. . . ) military strength, etc.
Circular Uniform Motion
Distinguish speed v
(a scalar) from velocity v (a vector). velocity constant: linear motion
Uniform motion keeps
Uniform circular motion
keeps speed constant (circular motion)
c L.Frommhold
. p.20/14
Centripetal Acceleration
Accele
Work (in Physics)
In Physics Work is defined as
W = FA d cos
c L.Frommhold . p.21/21
No Work, but (Lots of) Sweat ?
A person standing at the bus
stop may get tired, but he is doing no Work,
W = FA d cos
because d = 0.
Even if he were walking
home, W = 0
Definition of Momentum
The momentum of a particle is defined as
p=mv
Momentum is a vector Newton's 2nd law F = m v/t may be rewritten
p F = t
provided mass does not change with time.
Actually, this is the correct form of the 2nd law
c L.Frommhold
. p.18/1
The Conditions for Equilibrium
Expect static equilibrium whenever aceleration
Fnet = 0 net = 0
a = cfw_ax ; ay ; az and angular acceleration are zero,
The first of these equations gives you up to three
conditions (for x, y , and z components); the lower