1 Fisica 1 per Biotecnologie Introduzione Lun h 10:30 Mer h 10:30 Gio h 10:30 Alessandro De Angelis E-mail [email protected] Ricevo il mercoledì,

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Fisica 1 per BiotecnologieIntroduzione

Lun h 10:30Mer h 10:30 Gio h 10:30

Alessandro De Angelis E-mail [email protected] il mercoledì, 8:30-9:30

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Grantecan

MAGIC and its Control House

Telescopio Nazionale Galileo

MAGIC

La Palma, IAC28° North, 18° West

MAGIC

MAGIC

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www.fisica.uniud.it/~deangeli/biotec Obiettivi: Scopo del corso è di fornire gli elementi di base della fisica

generale.

Struttura: Il corso si svolge nel I periodo del I anno, con 22 lezioni distribuite in tre unità di 90 minuti ogni settimana. Nella pagina Web del corso e' pubblicata una versione aggiornata della struttura dettagliata delle lezioni (vedi tabella a pie' di pagina).

Programma: Unità di misura. Cinematica. Forze in natura: gravitazione, elettromagnetismo. Dinamica. Energia. Oscillazioni; cenni sul moto ondulatorio e sulle onde elettromagnetiche. 

Testo: Serway e Jewett - Principi di Fisica vol. 1, ultima edizione, EdiSES; appunti di lezione (che non sostituiscono il testo). Gli appunti di lezione e una selezione dei compiti degli anni precedenti sono reperibili nel sito del materiale didattico.

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www.fisica.uniud.it/~deangeli/biotec Titolare: Il titolare del corso si chiama Alessandro De Angelis. Riceve

nell'orario riportato su SINDY, o su appuntamento scrivendo a [email protected]. Melisa Rossi contribuisce al corso.

Valutazione: Nella sessione d'esame (due appelli) che segue il corso il voto proposto e' dato dal voto di un accertamento finale (valutato fino a 30 punti) cui viene aggiunto un bonus da 0 a 6 punti basato sulla valutazione dei compiti per casa. Lo studente che abbia superato la prova riportando un voto complessivo non inferiore a 18/30 supera l'esame. Nelle sessioni successive (un appello a Luglio e uno a Settembre) l'esame consta di una prova scritta che include domande di teoria, o di un orale che include esercizi.

Consigli: Procurarsi il libro di testo ben prima dell'inizio del corso, magari sfogliarlo quando

non si sa che fare... Dare un'occhiata agli argomenti della lezione successiva (il programma lezione

per lezione e' dettagliato nella pagina Web del corso) Studiare regolarmente ogni giorno quanto svolto in classe e svolgere gli esercizi

relativi.

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(…)

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About Physics

Provides a quantitative understanding of

phenomena occurring in our universe

Based on experimental observations and

mathematical analysis

Used to develop theories that explain the

phenomena being studied and that relate to

other established theories

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What is Physics? Model Building

A model is a simplified substitution for the real problem that allows us to solve the problem in a relatively simple way Make predictions about the behavior of the system

The predictions will be based on interactions among the components and/or

Based on the interactions between the components and the environment

As long as the predictions of the model agree with the actual behavior of the real system, the model is valid

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Particle Model

The particle model allows the replacement of an extended object with a particle which has mass, but zero size

Two conditions for using the particle model are The size of the actual object is of no consequence in the

analysis of its motion Any internal processes occurring in the object are of no

consequence in the analysis of its motion

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Theory and Experiments

Should complement each other When a discrepancy occurs, theory may be

modified Theory may apply to limited conditions

Example: Newtonian Mechanics is confined to objects traveling slowly with respect to the speed of light

Used to try to develop a more general theory

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Standards of Quantities

SI – Système International The system used in this course Consists of a system of definitions and standards to

describe fundamental physical quantities

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Time: second, s Historically defined as 1/86400 of a solar day Now defined in terms of the oscillation of radiation

from a cesium atom Some approximate time intervals, in s

Age of the Universe 5 1017

Since the fall of Roman Empire 5 1012

Your age 6 108

One year 107

One lecture 5 103

Time between two heartbeats 1

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Length: meter, m The “human-scale” definition: 1/10000000 of the

distance between the North Pole and the equator,

through Paris Length is now defined as the distance traveled by light

in a vacuum during a given time (~1/3 10-8 s) See table 1.1 for some examples of lengths

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Mass: kilogram, kg

The mass of a specific cylinder kept somewhere in Paris

See table 1.2 for masses of various objects

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Number Notation

Separation between units and decimals: dot (.) When writing out numbers with many digits,

spacing in groups of three will be used No commas, no dots

Examples: 25 100 5.123 456 789 12

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Reasonableness of Results

When solving problem, you need to check your answer to see if it seems reasonable How many molecules in a liter of milk?

Reviewing the tables of approximate values for length, mass, and time will help you test for reasonableness

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Systems of Measurements, SI Summary

SI System Almost universally used in science and industry Length is measured in meters (m) Time is measured in seconds (s) Mass is measured in kilograms (kg)

IT’S A LAW

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Prefixes Prefixes correspond to powers of 10 Each prefix has a specific name Each prefix has a specific abbreviation The prefixes can be used with any base units They are multipliers of the base unit Examples:

1 mm = 10-3 m 1 mg = 10-3 g

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Fundamental & Derived Quantities

In mechanics, three fundamental quantities are used Length Mass Time

Will also use derived quantities These are other quantities that can be expressed as a

mathematical combination of fundamental quantities Density is an example of a derived quantity; It is defined as

mass per unit volume

Units are kg/m3Vm

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Dimensional Analysis Technique to check the correctness of an equation or to assist

in deriving an equation. Dimension has a specific meaning – it denotes the physical nature of a quantity

Dimensions (length, mass, time, combinations) can be treated as algebraic quantities

Add, subtract, multiply, divide

Both sides of equation must have the same dimensions Dimensions are denoted with square brackets

Length – [L] Mass – [M] Time – [T]

Cannot give numerical factors: this is its limitation

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Dimensional Analysis, example

Given the equation: x = 1/2 a t2

Check dimensions on each side:

The T2’s cancel, leaving L for the dimensions of each side The equation is dimensionally correct There are no dimensions for the constant

][][][

][][ 2

2LT

T

LL

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Conversion of Units

When units are not consistent, you may need to convert to appropriate ones

Units can be treated like algebraic quantities that can cancel each other out

Always include units for every quantity, you can carry the units through the entire calculation

Multiply original value by a ratio equal to one The ratio is called a conversion factor

Example

km/h 361h

3600s

1000m

1km m/s 10

km/h ?m/s 10

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Order of Magnitude

Approximation based on a number of assumptions May need to modify assumptions if more precise results are

needed

Order of magnitude is the power of 10 that applies In order of magnitude calculations, the results are

reliable to within about a factor of 10

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Uncertainty in Measurements

There is uncertainty in every measurement, this uncertainty carries over through the calculations Need a technique to account for this uncertainty

We will use rules for significant figures to approximate the uncertainty in results of calculations

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Significant Figures A significant figure is one that is reliably known Zeros may or may not be significant

Those used to position the decimal point are not significant To remove ambiguity, use scientific notation

In a measurement, the significant figures include the first estimated digit

0.0075 m has 2 significant figures The leading zeroes are placeholders only Can write in scientific notation to show more clearly: 7.5 x 10-3 m for 2

significant figures 10.0 m has 3 significant figures

The decimal point gives information about the reliability of the measurement 1500 m is ambiguous

Use 1.5 x 103 m for 2 significant figures Use 1.50 x 103 m for 3 significant figures Use 1.500 x 103 m for 4 significant figures

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Operations with Significant Figures

When multiplying or dividing, the number of significant figures in the final answer is the same as the number of significant figures in the quantity having the lowest number of significant figures. Example: 25.57 m x 2.45 m = 62.6 m2

The 2.45 m limits your result to 3 significant figures

When adding or subtracting, the number of decimal places in the result should equal the smallest number of decimal places in any term in the sum. Example: 135 cm + 3.25 cm = 138 cm

The 135 cm limits your answer to the units decimal value

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Rounding

Last retained digit is increased by 1 if the last digit dropped is 5 or above

Last retained digit is remains as it is if the last digit dropped is less than 5

Saving rounding until the final result will help eliminate accumulation of errors

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Coordinate Systems

Used to describe the position of a point in space

Coordinate system consists of A fixed reference point called the origin Specific axes with scales and labels Instructions on how to label a point relative to the

origin and the axes

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Cartesian Coordinate System

Also called rectangular coordinate system

x- and y- axes intersect at the origin

Points are labeled (x,y)

3 coordinates (x,y,z) are enough to define the position of a particle in space

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Polar Coordinate System

Origin and reference line are noted

Point is distance r from the origin in the direction of angle , ccw from reference line

Points are labeled (r,)

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Polar to Cartesian Coordinates

Based on forming a right triangle from r and

x = r cos y = r sin

r is the hypotenuse and an angle

22 yxrxy

tan

Cartesian to Polar