Transcript Review - HayonPhysics

Standards/Plan
Standards
Standards
Standards
Processes
Standards
Standards
WARM UP
1)
Simple Harmonic Motion (SHM)
1)
Simple Harmonic Motion (SHM)
Warm Up
2) A block is pushed along a horizontal, frictionless
surface, with a horizontal Force that varies as a
function of time as shown in the graph here. The
mass of the bloc is 3kg. If the block was at rest at
time t=0, what is the speed of the block at time t=3?
Warm up 2
Warm Up
3) Three blocks of mass m, 2m, and 3m are placed
adjacent to each other on a frictionless horizontal
surface as shown above. A constant force of
magnitude F is applied to the right. Which of the
following statements is true?
Warm Up
Warm Up
4) Two masses, M>m, are connected by a light string
hanging over a pulley of negligible mass. When the
masses are released from rest, the magnitude of the
acceleration of the masses is?
Warm Up
5) A mass of 2.0kg is attached to the end of a light cord
to make a pendulum 5.0m in length. The mass is
raised to an angle of 53 relative to the vertical, as
shown, and released. The speed of the mass at the
bottom of the swing is:
Warm Up
6) A cannon is mounted on a cart, and
carrying a cannonball. The total
mass of the cart, cannon, and ball is
M, and the cart is rolling with no
friction at a velocity v in the positive
direction as shown above. The ball,
of mass m, is fired with a velocity
vball in the positive x direction. What
is the velocity of the cart and
cannon after the ball is fired?
Warm Up
6)
Warm Up

Awesome Gas Video
 NO WARM
UP!
Warm Up
7) A student lies on a rigid platform of negligible mass, which is in turn
placed upon two spring scales as shown above. The left scale at
position 0 reads 200N, and the scale on the right at position L, reads
300N. Find the value of X in terms of L.
a.
b.
c.
d.
e.
X = 1/2 L
X = 2/5 L
X = 3/5 L
X = 3/4 L
X = 4/5 L
PIVOT
POINT
Warm Up
8)
Warm Up
8)
Warm Up
9) A pendulum driven clock,
located on earth, is set into
motion by releasing its 10m
long simple pendulum from a
maximum angle of less than
10° relative to the vertical. At
what approximate time t will
the pendulum have fallen to a
perfectly vertical orientation?
(Use 10 for g)
Warm Up
Warm Up
10) By visual
inspection, order the
PV diagrams shown
from the most
negative work done
on the system to the
most positive work
done on the system.
A. a,b,c,d
B. a,c,b,d
C. d,b,c,a
D. d,a,c,b
Lesson
Announcements
Pass Back Fluids Quiz:
Thermo Quiz Friday!
What are important quantities in
thermodynamics?

Pressure  Atoms colliding w/ wall of a container

Temperature  How fast atoms move

Volume  How much space atoms “need” to move freely

Number of molecules Really big numbers
Kinetic Theory of Gases Assumptions
for an IDEAL GAS
1) Atom are bouncy:
Elastic collisions between
atoms
2) Atoms are spread out:
Far away unless colliding
3) Atoms are random:
No preferred direction of
motion (means pressure is
equal everywhere in a
container
Calculation – Units to use

Pressure  ALWAYS Pascals (N/m2 )

Temperature  ALWAYS Kelvin (273 + oC)

Volume  ALWAYS m3

Number of molecules moles or molecules
Moles = Molecules/6.02E23
R
= 8.31J/molK
 Kb = 1.38 E-23 J/K
(Liters/1000)
Equation’s so far
1.
2.
3.
PV = nRT
PV = NkbT
P1 V1 / T1 = P2 V2 / T2
4.
5.
M is molar mass
Energy of a Gas
Energy Type
U = Internal
energy
Q = HEAT
W = Work
ΔU = Q + W
2. U = 3/2 nRT
3. U = 3/2 PV
1.
(+)
(-)
Temp INCREASE TEMP DECREASE
HEAD ADDED
HEAT REMOVED
GAS CONTRACTS
(WORK ON)
GAS EXPANDS
(WORK BY)
Gas Process

The thermodynamic state of a gas is
defined by pressure, volume, and
temperature.

A “gas process” describes how gas gets
from one state to another state.
Isothermal Process
(constant temperature)
P
Hayon: Pull plunger up from
halfway (slowly)
T1
DT = 0 (constant T)
V
Hayon: Heat up the tank
while allowing plunger to
move
Isobaric Process
(constant pressure)
P
Isobaric Expansion
Isobaric Contraction
DP = 0 (constant P)
V
Isometric Process
Hayon: Push to the top and
then heat up or push to the
bottom and then cool down
(constant volume)
P
NO WORK
POSSIBLE!!
DV = 0 (constant V)
V
Adiabatic process
(PERFECTLY insulated)
P
T
NO HEAT IS
TRANSFERED
ΔU = W
isotherm
adiabat
Q = 0 (no heat enters or leaves)
V
Example Problem
0.25 moles of a gas are kept at 1150K. The
gas undergoes adiabatic expansion,
reaching a final temperature of 400K. How
much work was done on or by the gas?
U = 3/2 nRT
Hayon: Test (remember area)
and don’t use 1 way valve
Using PV Diagrams
WORK = Area under a PV Diagram
P
(+) = Contract
(-) = Expand
200kpa
100kpa
250m2
300m2
V
Free Response Problems

FR #1 as an Example

Web Assign: Thermo Assignment #2

Then skip #2 and go to the back