PH6_L1 1

Physics I: PH1010

Mahaveer K. JainPhysics Department

R.No. HSB213AEPABX: 4880

Email: mkjain@iitm.ac.in

PH6_L1 2

• Welcome to IIT Madras and welcome to PH 1010 Course

• A bit of Introduction about the Course

• A few Dos and Don’ts in this Course

PH6_L1 3

Please remember that ALL of you equally competent – So you are all hereYou all have done enough of Physics and Solved very many problemsAll of you have toiled for the JEE and other ExaminationsIf you are not intelligent, you will not be hereYou are here with a great ambition of learningYou are all here with a specific purpose : of getting a good 

B Tech Degree of world standard We want to see you as GOOD TECHNOCRATSThe foundation of Good Technology is clear basic PhysicsThis Physics we learn in this course PH 1010.

3

PH6_L1 4

Our Class Time Table :

Class Room :  CRC 102Monday : Lecture/TUTORIAL  :  6th Hour  : 2 – 2:50 PMTuesday : Lecture  :  8th Hour    : 3:50 –4:40 PMWednesday : Lecture  :  8th Hour    : 3:50 –4:40 PM

We propose to conduct : MID SEMESTER exam (exact date will be announced shortly)

End Semester exam:   NOVEMBER 25  (THURS DAY)

Tutorial  is problem solving classYou will be given the Tutorial sheets ONE WEEK in advanceYou have to come prepared to the class and may be one of you will be asked to solve the problems  

4

PH6_L1 5

In case of any need and necessity, we may ask you to come for an extra class On  THURSDAY 7th Hour (D2 Slot) : 2:55‐3:45 Hrs  

Two class representative

All Course related material :SyllabusLecture presentationsProblem sheetsSolutions 

will be posted at :  

http://www.physics.iitm.ac.in/index_files/courses/PH1010.html

5

PH6_L1 6

SyllabusVelocity, Momentum, Force, Torque, Field [Electric,

Magnetic, Gravitational,…………….], etc.Polar coordinates – Symmetry [cylindrical, spherical]Unit vectors in Cartesian and polar coordinates.Conservative vector fields and their potential

functions: examples (gravitational and electrostatic)

Gradient of a scalar fieldEquipotentialsStates of EquilibriumWork and Energy, Conservation of energyMotion in a central force and conservation of

angular momentum

PH6_L1 7

SyllabusContinuity equations and conservation principles for matter,

energy and electrical charge.Flux: divergence of a vector; Applications: Fluid DynamicsGauss’ theorem Physical applications in gravitation, Fluid Dynamics and

electrostaticsIrrotational versus rotational vector fieldsPhysical significance of circulation, CURL of a vector fieldStoke’s theorem, Applications: Magnetostatics, Electrostatics

and Fluid Dynamics

PH6_L1 8

syllabusOscillatory motionWave motion in one dimensionWave equation and travelling wave solutionsWave velocity, group velocity and dispersionShallow water wavesWave equation in three dimensions, spherical waves

PH6_L1 9

ATTENDANCEWe teach conceptsThere is no single Text book This is the reason why YOU SHOULD ATTEND

ALL THE CLASSES 100% attendance is an ABSOLUTE requirement

***If you pass an examination in the second attempt (because of either U or W grade in the first attempt), it WILL be recorded so in your grade sheets***

PH6_L1 10

References

1. Kittel C, Knight W.O and Ruderman M.A, Mechanics Berkeley Physics Course, Vol.1, Tata McGraw-Hill

2. Purcell E.M, Electricity and Magnetism, Berkeley Physics Course, Vol.2, Tata McGraw-Hill

3. Crawford F.S, Waves and Oscillations, Berkeley Physics Course, Vol.3, Tata McGraw-Hill

4. The Feynman Lectures on Physics, Vol.1 and Vol.25. Davis D., -Classical Mechanics6. Kleppner and Kolenkow- An Introduction to Mechanics7. Schaum’s outline series- Theory and problems of vector analysis

PH6_L1 11

As you all know:

There are only FOUR forces in Nature :

‐ Gravitational‐ Electro‐magnetic‐ Strong Nuclear force ‐Weak Nuclear force

If you know how many forces are acting on a body, you can calculatethe motion of the body at any given time.

But, we encounter forces which we do not know : Frictional force

Friction is important for motion (without friction, the body slips or skids)

Friction is a NON CONSERVATIVE force.

11

PH6_L1 12

What is Conservative force? 

What is a NON‐CONSERVATIVE Force? 

How do you define it ? 

Force methods of solving problems in Physics is rather limited.

So, what is the next alternative?

Energy methods:

How many energies are there ? Potential and Kinetic

What is conservation of energy ? 

What is the relation between energy and force ?  

12

PH6_L1 13

If a force is applied to move this table:

I am applying the force, but the table is not moving at all 

Tell me, how much work is done ?

The earth is moving round the sun : how much work is done? What is the force involved? 

When an electron is moving round the nucleus, how much work is done?What is the energy involved?  Where it comes from ? 

If I move an object in any arbitrary direction and if I come to the same point as I started, how much work is done? How much energy is spent? 

13

PH6_L1 14

Imagine a body is moving under the influence of a force :Say, an electron is moving under the influence of 

electric and magnetic forces

Describe the motion.

How  are you applying the Electric field  + and  ‐ ve platesHow are you applying the magnetic field ? 

N – S or S – N w.r.t to what 

14

PH6_L1 15

Direction MUST be specified to state your problem.

The body can move with uniform velocity or withuniform acceleration

How do you describe the motion ?  

Direction should be specified to describe the motion?

How do you express the direction?  

15

PH6_L1 16

If the body is moving with constant acceleration and if the frame of reference  also  moves with same acceleration, how do you describe the  motion? 

What is an INERTIAL Frame? 

What is Newtonian space ? 

How many coordinates you require to specify a body? 

What is a generalized coordinate ? 

16

PH6_L1 17

Types of EnergyExample: Falling BodyExample: Falling Body• Kinetic Energy

EEK K = = mvmv22/2/2• Potential Energy

EEP P = = mghmgh• Rest Energy

EER R = = mcmc2

h

m

v

2

PH6_L1 18

Classical PhysicsPicture prior to 20th Century:Picture prior to 20th Century:•• EnergyEnergy and mattermatter were separate and distinct substances. 

• Although appearing continuous to the naked eye, matter was composed of discrete, localized atoms.atoms.

•• LightLight was a form of electromagnetic wave, the vibration of a continuous cosmic field, the aether, and regarded as a form of "pure energy.""pure energy."

•• GravityGravity was a continuous action‐at‐a‐distance field.

PH6_L1 19

Modern PhysicsCurrent picture:Current picture:Energy and matter are the same stuff: same stuff: 

E = mcE = mc22• The discretediscrete nature of matter is confirmed. Energy is also 

discrete.• There is no evidenceno evidence for an aether or any other continuous 

medium in universe. Light is composed of particulate matter: photons.photons. Fields are composed of discrete particles ("quanta").

• General relativity explains gravitygravity in terms of the curvature of curvature of spacespace rather than as a force field.

PH6_L1 20

Molecules

Matter

Atoms

Nuclei and Electrons

Quarks

Protons and Neutrons

PH6_L1 21

Let us come back to the problem of Forces :

21

PH6_L1 22

The Standard Model of Forces Forces result from the exchange of particles:Forces result from the exchange of particles:• Electromagnetism photonphoton• Strong nuclear     gluons (8)gluons (8)• Weak nuclear     weak bosons (4)weak bosons (4)

(No quantum theory of gravity as yet)(No quantum theory of gravity as yet)

While these force particles are described by quantum fields in the theory, no continuous no continuous medium,medium, like the aether, is involved.

PH6_L1 23

The CosmosMass BudgetMass Budget

RadiationRadiation 0.005 %0.005 %

Ordinary visible matterOrdinary visible matter 0.5 %0.5 %

Ordinary Ordinary nonluminousnonluminous mattermatter 3.5 %3.5 %

Exotic dark matterExotic dark matter 26 %26 %

Even more exotic dark Even more exotic dark ““energyenergy”” 70 %70 %

Nature of dark matter and dark energy Nature of dark matter and dark energy still unknown.still unknown.

But not But not ““immaterialimmaterial”” since carry masssince carry mass..

PH6_L1 2424

PH6_L1 25

So, it is all the same whether we talk of

- Forces

- Matter

- Energy

It is only the language of Physics.

The Conservation of Energy, Conservation of Matter and Conservation of Charge are of fundamental importance

These are the basic laws of Nature

These basic laws of Nature can also be Derived from Symmetry

.

25

PH6_L1 26

Transformations and InvarianceTransformations and Invariance

• Transformations• Changes from one reference frame to another.

InvarianceA physics equation is invariant if it

does not change under a transformation. X

y

X

y

Covarient : The formula looks the same but meaning of each term is different