PHL105Y5 Lecture : Descartes Notes

48 views2 pages

coralguinea-pig485

5 Oct 2011

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

If s knows that p, then it isn"t possible that s is mistaken in believing that p. It is possible that s is mistaken in believing that p: therefore s doesn"t know that p. If i have a reason to doubt p, then i do not know that p. Foundationalism: to reject everything that you have ever known and start from the beginning. Demolish the foundations of the house that you built and build it again from only things you are certain of. Anything that we have a reason to doubt is to be discarded. Radical skepticism: neither my beliefs about the external world nor my belief that 2+2=4 are certain. 1the senses deceive us about small and distant objects (illusions) 2i may be a madman who thinks i have true perceptions. 4god may have made me in a way that i am systematically deceived about what goes on around me. Possible world 1: god gives me true beliefs.

Related Questions

a.) A hockey puck is observed to be sliding along a flatfrictionless surface at a speed of 4 cm/min. There is no net forceacting on the puck. Assuming it doesn't smash into anything, howfast will the puck be going 17 min later?
cm/min

b.) An object is accelerating. Which one of the followingstatements is true?
The object must be speeding up.
Gravity must be causing the object to accelerate.
The object must be changing directions.
The object must be slowing down.
There is a net force acting on the object.

c.) A 100 kg block weighs 220 lb on Earth. If the block weretransported to a planetary body that had a smaller free fallacceleration (as compared to Earth), which one of the followingwould be true?
The block would have the same weight and a smaller mass.
The block would have the same mass and a bigger weight.
The block would have the same mass and the same weight.
The block would have the same weight and a bigger mass.
The block would have the same mass and a smaller weight.
d.) What does it mean (in physics) to say that a quantity isconserved?
It means that the quantity is not being used.
It means the total amount is zero.
It means the total amount never changes.
It means it's being saved up.

e.) At a certain point in time, the total energy of a closed systemis observed to be 176 J. Which one of the following statements istrue?
Three hours later the energy of the system is 352 J.
Four hours later the energy of the system is 88 J.
All of the energy must be kinetic if the objects are moving.
Twelve hours later the energy of the system is 176 J.
Some of the energy must be potential.

g.) Which of the following statements are impossible? Choose allthat apply.
The parked truck had 8770 J of KE.
The scooter had 0 J of KE and 0 kgÂ·m/s of momentum.
A ball moving in a circle had 0 N of net force acting on it.
A box had an acceleration of 0 m/s2 while a net force of 311 Nacted on it.
Jack exerted 18 N of force due east on a cart. As a direct result,the cart exerted 18 N of force due west upon Jack.
A toothpick exerts a smaller gravitational force upon the Moon thanthe Moon exerts upon it.

a.) Two balls make up a closed system. Ball A has 701 J of energyand ball B has 78 J. After they collide, ball A has 665 J. How muchenergy does ball B have after they collide?
J

b.) An asteroid and a comet collide head on. Prior to thecollision, the asteroid has a momentum of 700,000 kgÂ·m/s up and thecomet has a momentum of 800,000 kgÂ·m/s down. After the collisionthe asteroid has a momentum of 750,000 kgÂ·m/s down. After thecollision, what is the comet's momentum?
kgÂ·m/s
North
South
East
West
Up
Down
Left
Right
No direction because the comet has stopped

c.) How much does a 28 kg object weigh on Moon? Please feel free toreference the Solar System Data table located at the beginning ofUnit II.
______N

d.) A 660 N net force acts on a 42 kg object. Determine theobject's acceleration.
_____m/s2

e.) Calculate the gravitational force between a 657 kg object(resting on Earth) and the Moon. The mass of the Moon is 7.347Ã1022kg and the distance between the object & the Moon is 3.844Ã108m.
____N

Vapor cycles
5EM - Thermodynamics
September 2010
1 The T-S diagram
The temperature-entropy diagram is an alternative to the well knownpressure-
volume diagram. Before using it to analyze different vapor cycles,we need
to understand it properly.
1. Plot the following transformations for ideal gases in a T-Sdiagram
(a) Isothermal expansion
(b) Isobaric expansion
(c) Isometric heating
(d) Reversible adiabatic expansion
(e) Irreversible adiabatic expansion
2. Repeat the last question, but this time do it for a realsubstance,
starting in the compressed liquid1 region and ending in thesuperheated
region, when possible. Indicate the boundaries of eachregion.
3. We know that under certain circumstances the area under theplot
in a P-V diagram represents the work performed during theprocess.
What does it represent in this case? Under what assumptions isyour
answer true? Compare examples 6.1 and 6.2.
2 Thermal machines
We understand by thermal machine a device capable of transformingther-
mal energy (heat) into mechanical energy (work). We already knowthat
these machines have a limited efficiency which, in the two-sourcesmodel, is
obtained by Carnotâs cycle.
(Compressed liquid is sometimes also called subcooled liquid)
2.1 Carnot cycle
This cycle, although efficient, is impractical. To begin with, theextreme
temperatures of the cycle should be within the sources temperaturesfor a
finite heat flow to exist.
1. Given the temperature of the sources, draw the cycle accordingto the
named limitation.
2. Show that this leads to lower efficiency than the theoreticallimit.
3. Assume that heat flow from/to the sources is proportional to thetem-
perature difference between them and the working fluid, anddemon-
strate that a higher power output is related to a decreasedefficiency.
2.2 Rankine cycle
Out of the several practical possibilities, Rankine cycle and itsvariations is
widely used, especially for electric power generation.
1. Draw the basic cycle in a T-S diagram and explain it.
2. What does the efficiency of the cycle depend on? Comparewith
Carnotâs.
3. What are the differences between the ideal cycle and the realone?
4. Describe how it is modified by superheating and/or reheating.Explain
te benefits.
2.3 Problems
After answering the previous questions solve the followingexercises from the
book: 8.2, 8.4, 8.5, 8.13, 8.19, 8.20
3 Frigorific machines
3.1 Reverse Carnot cycle
We have already studied Carnot cycle in detail as the ideal thermalmachine.
Now we will take is as the starting point to understand thecharacteristics
of frigorific machines.
1. Draw the ideal cycle in a T-S diagram and explain it.
2. Show that this cycle has a theoretical efficiency Ã =Tcold/Thot-Tcold
3. What are the difficulties in implementing such cycle in actualdevices?
3.2 Actual refrigerators
1. Why is the turbine replaced by an expansion valve in mostcases?
2. Plot the actual cycle and explain the differences with the idealcase.
3. How do cascade and multistage systems improve the performanceof
the refrigerator?
4. What aspects are important in the choice of a refrigerant fluid?Justify
3.3 Problems
After answering the previous questions solve the followingexercises from the
book: 10.2 10.7, 10.8, 10.9, 10.22, 10.23 10.1D

PHL105Y5 Lecture : Descartes Notes

Document Summary

Get access

Related Documents

PHL105Y5 : Renes Descartes Meditation 1 and 2

PHL105Y5 Study Guide - Final Guide: Descriptive Knowledge, Ontological Argument

PHL105Y5 Study Guide - Tyrant, Deductive Reasoning, Everytime

Related Questions