# Udacity’s ‘Introduction to Physics’ course

Took ‘Introduction to Physics’ course at Udacity. It is a beginner level course and I have skimmed through most of it. But what kept me going till the end is the extremely engaging way in which it is taught. Every lesson, you take one important Physics problem and try to solve it. You make progress in small steps by learning required techniques and mathematics. Interactive nature of the platform always makes you think by asking questions before introducing new concepts. On top that, all this is linked with the history of the problem, who solved it and how?

The course has 7 lectures:

### Lecture # 1: Circumference of Earth

The Greek philosopher, Eratosthenes (276 BC – 195 BC), was the first person to calculate the circumference of earth with remarkable accuracy. He used geometry and trigonometry to figure this out.

He only needed to take following measurements for his calculation:

• Length of the shadow cast by an object A at noon at location X.
• Height of the object A.
• Distance of location X to the nearest location where sun doesn’t cast any shadow at noon.

See the diagram and link below for details.

### Lecture # 2: Speed of freely falling object

Aristotle had following view on this:

• Objects fall at constant speed.
• Speed is directly proportional to mass of object.

It was Galileo who found that the distance covered by a falling object is directly proportional to the square of time it has been falling (i.e. objects fall with constant acceleration irrespective of their mass).

### Lecture # 3: What causes motion?

The prevalent view before Galileo and Newton was Aristotelian. According to which there is one set of laws governing heavenly bodies and a different set for bodies on earth.

Newton through his laws of motion asserted that both heavens and the earth follow the same laws. And the apple falling from a tree or moon orbiting the earth do so under the influence of same force.

### Lecture # 4: Keeping Holland Dry

This lecture is about Archimedes Screw and the basic principles behind its working. It builds on the understanding of force from previous lectures and introduces simple machines: Inclined Plane, Pulley and Lever. Simple machines enable us to trade off the force required to lift or move things with the distance. For example, using an inclined plane to move something to a higher level will require less force but we need to push it for a longer distance.

Next, the concepts of Work, Energy and Power are introduced.

• Work = Force * Distance
• Work = Change in Energy
• Power = Work / Time

Finally, the Law of Conservation of Energy is discussed with the example of roller coaster ride. During the ride, energy changes its form between kinetic and potential with some of the energy lost due to friction as heat.

### Lecture # 5: Lost at Sea

Problem of this lecture is how to measure latitude and longitude?

Latitude is relatively easier to calculate while longitude is much trickier.

When sun is at the highest point in the sky and it is equinox, the latitude can be calculated as explained in the first lecture.

For calculating Longitude, we need to keep track of time. Galileo attempted to measure time by observing transit of Jupiter’s moon but the idea was not very fruitful due to the difficulties involved.

The answer lies in Simple Harmonic Motion.

Elastic Potential Energy

k = Spring Constant

Lecture discusses the discovery of Pendulum by Galileo and invention of Pendulum Clock by Christiaan Huygens.

Longitude can be measured by comparing the time on ship to the time of a known location. Pendulum clocks can be used to reliably measure time and hence calculate longitude.

### Lecture # 6: Lightning Strikes

Lightning is an electrical phenomenon. This was not very clear in 18th century. The link between lightning and electricity was there in the literature but it was Benjamin Franklin (17-Jan-1706  to  17-Apr-1790) who emphasized this link and developed lightning rods which prevented buildings from burning due to lightning strikes.

This lecture talks about basics of electricity with particular focus on lightening rod and how it grounds the electric current keeping buildings safe.

### Lecture # 7: Special Relativity

This is brief teaser to Special Relativity explaining the following two postulates of the theory and how they lead to bizarre conclusions like time dilation.

• Laws of Physics are same in all inertial frame of reference
• Speed of light constant regardless of the frame of reference

de Sitter double star experiment is explained as test of Special Relativity.

It concludes with a final exam where you can test your problem solving skills using the knowledge gained through the course. There are couple of bonus lectures also about ‘simple harmonic motion’ and ‘why can’t we open windows on an airplane’.

# Read ‘Physics of the Impossible’ by Michio Kaku

Physics of the Impossible: A Scientific Exploration into the World of Phasers, Force Fields, Teleportation, and Time Travel’ explores the popular science fiction concepts in the light of hard scientific facts. In doing so the author explains scientific theories in a way that is very engaging and comprehensible for a layman. Along the way author alludes to interesting details about how the modern scientific theories developed overtime and what are current areas of research which could make the impossible possible. All analyzed concepts are categorized based on how long it might take for human civilization to achieve them if ever.

In my opinion, this is a definite read for only one interested in science or science fiction.

# Completed ‘Machine Learning’ from Coursera

Completed ‘Machine Learning’ course offered by Andrew Ng, Associate Professor of Computer Science, Stanford University. This course was offered through Coursera.org

The course started on 23rd April and the duration was 10 weeks. It was an exhilarating opportunity to learn about this cutting edge field. The distinctive feature of the course was weekly programming assignments in Octave which were automatically evaluated by Coursera.org. Also the course was very well organized, we can expect that as it was offered by the co-founder of Coursera.

# Completed ‘Introduction to Logic’ from Coursera

Completed ‘Introduction to Logic’ course offered by Michael Genesereth, Associate Professor, Stanford University. This course was offered through Coursera.org

The course started on 23rd April and the duration was 7 weeks. It was very well structured and the online proof editor were a treat to work with. The course also helped to the understand some of the concept in Compilers design.

# Completed ‘CS101 (Introduction to Computing Principles)’ from Coursera

Completed the ‘CS101 (Introduction to Computing Principles)’ course offered by Nick Parlante, Lecturer in Computer Science, Stanford University. The course was offered online through Coursera.org

The course started on 23rd April 2012 and went on for 6 weeks. It was a introductory course and meant for people from non-IT background. Despite having two degrees in Computers, I still went for it to explore the Coursera platform. I found it to be such a fun platform to learn, thoroughly enjoyed it.

# Free online courses from Top Universities

A revolution is underway in higher education. Top universities are offering their courses online for free through initiatives like:

Coursera – Launched by two Standard University professors: Daphne Koller and Andrew Ng
Udacity – Co-founded by Google Executive and Standard professor Sebastian Thrun
edX – Joint venture by MIT and Harvard

We already have a lot of video lectures from top universities on YouTube and iTunes. But these new initiatives are different, they are a game changer. They are able to create a virtual classroom environment which is attracting thousand of people from all over the world.

First the course starts at a particular time and you have to enroll for it. That means a lot of students take the course at the same time and they are able to discuss and help each other through forums.

Secondly rather than hour long video lectures, each video is about 10 minutes long covering one concept at a time. This really suits the online self-paced learning model.

Students are required to submit review questions and assignment each week. This gives a sense of progress and acheivement which is vital to keep you going back to the virtual classroom every week. Statement of Accomplishment of issued at the end if you get the passing score.

I have enrolled in some of the courses from Coursera and having a wonderful time 🙂

# Boomerang: Travels in the New Third World (book)

The book is about the travels of Micheal Lewis to western countries which are worst affected by the recent financial crisis. It explores how the crisis has devastated Iceland, Greece and Ireland; and its impact on Germany and US.

The author sketches quite a few stereotypical characters from the countries he visited, I not sure how much they correspond to reality.

Overall, It is an interesting read.

# Microsoft Case Study for Disaster Recovery

In 2007, I was working at Engro Chemicals Pakistan as ‘Applications Lead Team’. We had a major fire disaster at Head Office which destroyed the whole building along with the IT data centre. One aspect of my work on disaster recovery was published by Microsoft as a case study on their website. Following is the link to microsoft website:

http://www.microsoft.com/india/casestudies/Case_Study_Detail.aspx?casestudyid=4000004068

Following is the case study in word document: EngroCaseStudy (source: www.microsoft.com)