Announcements
Ball rolling down an incline
Exam 2 covers up to Ch. 8.4 but concentrates on Ch. 5.4 to 8.4
Room Assign.
CAR 0100
NPB 1001
MCCC0100
Last name
ABBASI - KURTEK
KURTZ - PINCKET
PINEDA - YOUNG
How fast does it leave the
bottom of the incline?
Number
285
170
150
Review Thursday—clickers will not count.
From Supplemental Instructor (J.J.):
Help session tonight (Tuesday 11/10), none tomorrow (Veterans’ Day)
MAEB 229 from 5:20pm to 7:05pm.
Homework #9 will be posted Friday and due next Wednesday Nov. 18
h
Conservation of Mechanical Energy
(KEt + KE r + PE g + PE s )i = (KEt + KE r + PE g + PE s )f
+ mgh + 0
= mv2/2+Iω2/2 + 0 + 0
I=2mr2/5 and rω=v so Iω2/2= mv2/5
Giving: mgh = mv2/2+ mv2/5 = 7 mv2/10
0
+
0
Note m cancels out as usual
or
v= 10gh/7
Strength of materials
Something very bad happened
when it got a little cold
(just above freezing)
Challenger
Titanic
Quantitative characterization of mechanical
properties of materials
Density
Elastic Properties
ρ ≡
Stress is the force per unit area
causing the deformation
Strain is a measure of the amount
of deformation
The elastic modulus is the constant
of proportionality between stress
and strain
The density of a substance of uniform composition is
defined as its mass per unit volume:
m
V
3
Units are kg/m3 (SI) or g/cm (cgs)
1 g/cm3 = 1000 kg/m3
For sufficiently small stresses, the stress
is directly proportional to the strain
The constant of proportionality depends
on the material being deformed and the
nature of the deformation
Pressure
The force exerted
by a fluid on a
submerged object
at any point is
perpendicular to
the surface of the
object
P≡
F
N
in Pa = 2
A
m
Piston
Calibrated
Spring
Fig. 9-10, p.276
Pressure Units
Weight of the Atmosphere
Area A
h
m
Surface of Earth
F
F = mg = ρVg = ρAhg
F/A = ρhg = P
Liquid in a U- tube
Liquid in a U- tube
Patm
Patm
Patm
Patm
h1
h1
h1 = h2
h2
P = Patm + ρgh1
P = Patm + ρgh2
h2
P = Patm + ρgh1
Pressure and Depth equation
Pressure Measurements: Barometer
Po is normal
atmospheric
pressure
1.013 x 105 Pa
The pressure
does not
depend upon
the shape of
the container
P = Patm + ρgh2
Invented by
Torricelli (1608
– 1647)
A long closed
tube is filled
with mercury
and inverted in
a dish of
mercury