## What’s wrong with textbooks?

The Trials are approaching fast, you know you need to study! But reading textbooks and notes can be incredibly bland and mind-numbing. Sometimes the ideas in Physics are quite subtle, and incredibly difficult to grasp from just reading a paragraph.

## Video to the rescue!

That’s what makes video and animation so great! It helps you to see the actual physics behind a problem, and gives you a much deeper insight and understanding. I know I was very apprehensive about searching the internet for videos to help with HSC Physics. I questioned whether the videos I were watching were actually helpful. Was this content even assessable? Was I wasting my time, should I have spent the time just reading the textbook a few more times?

Absolutely not!

Some of the videos I watched were amazing, and really helped clear my doubts. I want to save you the time of having to search for great videos, so I’ve compiled a master list of videos I found incredibly helpful for the Space module.

## The Playlist

**Syllabus Dot Point:**Define weight as the force on an object due to a gravitational field**Common Misconception/Confusion:**What’s the difference between mass and weight? Don’t heavier items experience a larger gravitational force? So why don’t heavier items fall faster?**Why this video will help:**Derek Mueller of Veritasium Fame, insightfully explains the subtleties of mass, weight and inertia to hopefully answer all those questions above. Did you understand the previous video? Let’s make sure!

**Syllabus Dot Point:**Explain that a change in gravitational potential energy is related to work done.**Common Misconception/Confusion:**Isn’t work related to pushing an object, what has that got to do with gravitational potential?**Why this video will help:**In this video, Jeff goes back to the definition of Work to show you just how these two quantities are related, and then goes through some sample questions.

**Syllabus Dot point:**Define gravitational potential energy as the work done to move an object from a very large distance away to a point in a gravitational field.**Common Confusion/Misconception:**Why is there a negative sign in the formula?**Why this video will help:**John explains how it basically comes down to choosing a definition that makes sense and is consistent. How do we get a number to get bigger and bigger as we move away from the Earth, but be 0 at the end? Well, it has to start out negative! Click Here

**Syllabus Dot Points:**Describe the trajectory of an object undergoing projectile motion within the Earth’s gravitational field in terms of horizontal and vertical components. Describe Galileo’s analysis of projectile motion**Common Confusion/Misconception:**What did Galileo say about projectile motion? Why is vertical velocity constant, and why is vertical velocity changing? What are the implications of this?**Why this video will help:**Derek’s animation is incredibly clear and also entertaining. He outlines everything you need to know! Just click Here. Now you know how it works, how do you solve problems? Try this too.

**Syllabus Dot Point:**Explain the concept of escape velocity in terms of the gravitational constant and the mass and radius of the planet.**Common Misconception/Confusion:**Where does the formula for escape velocity come from? How do rocket’s escape? Remember, this whole concept of escape velocity applies to projectiles. E.g. the speed we must throw an object in order for it to escape. It does not include things like rockets and other such objects which can accelerate!**Video:**You can watch this https://www.youtube.com/watch?v=-uUsUaPJUc0 video from Doc Schuster. His brilliant use of colour and humour is just what you need to wrap your head around escape velocity, where it comes from and what it means.

**Syllabus Dot point:**Outline Newton’s concept of escape velocity**Common Misconception/Confusion:**How can something fall towards the earth forever? Why doesn’t it hit the ground?**Video:**This video has some humorous animation to help visualise just exactly how it all works.

**Syllabus Dot Points:**Analyse the changing acceleration of a rocket during launch in terms of the Law of Conservation of Momentum and the forces experienced by astronauts/ Discuss issues associated with safe re-entry into the Earth’s atmosphere and landing on the Earth’s surface (including “Identify that there is an optimum angle for safe re-entry for a manned spacecraft into the Earth’s atmosphere and the consequences of failing to achieve this angle”)**Why this video will help:**Sure you could read a textbook, but why not have astronauts who’ve actually been to space tell you exactly what it felt like! You can skip to around 7:30 if you’d like, where the discussion of descent begins. Click Here

**Syllabus Dot Point:**Discuss the effect of the Earth’s orbital motion and its rotational motion on the launch of a rocket**Common Misconception/Confusion:**When standing on Earth, you don’t really feel its rotation, how could it possibly make a difference to help launch a rocket.**Video:**If you’re having trouble visualising how we harness the rotation of the Earth, this video should help! It’s all about the rotation of the earth relative to the sun. Click Here

**Syllabus Dot Point:**Analyse the forces involved in uniform circular motion for a range of objects including satellites orbiting the Earth.**Common Misconception/Confusion:**If something is moving at a constant speed in a circle isn’t its acceleration 0?**No**. Remember acceleration is defined as a change in velocity, since we are moving in a circle our velocity is changing and so there is indeed an acceleration, and by Newton’s 2nd law there must be a force causing it!**Video:**This video should clear up any doubt you have about general circular motion.

**Syllabus Dot Point:**Define the term orbital velocity and the quantitative and qualitative relationship between orbital velocity, the gravitational constant, mass of the central body, mass of the satellite and the radius of the orbit using Kepler’s Law of Periods**Common Misconception/Confusion:**Where does Kepler’s Law of Periods, come from, what is it telling me?**Video:**Here is a derivation if you’re interested where it comes from. Click Here. Here’s an example animation showing Kepler’s third law in action: Click Here and here’s a sample problem and answer (try it yourself before playing the answer!): Click Here

**Syllabus Dot Point:**Define Newton’s Law of Universal Gravitation**Common Misconceptions/Confusion:**What is it? What does it tell us? Do you have an example?**Video:**Done, done and done! Click Here

**Syllabus Dot Point:**Identify that a slingshot effect can be provided by planets for space probes**Common Misconception/Confusion:**The slingshot effect is rather subtle, and many people misunderstand it. When you begin to orbit a body, you are pulled towards and speed up, but when you leave shouldn’t you lose that speed gained? So how does the effect actually work.**Why this video will help:**In this video a lot of misconceptions about the slingshot effect are tackled, as he meticulously explains just how it all works with some nifty animation. You’ll also see some real world examples of where scientists have used the slingshot effect. Click Here to Watch

**Syllabus Dot Point:**Outline the features of the aether model for the transmission of light. Describe and evaluate the Michelson-Morley attempt to measure the relative velocity through the aether. Gather and process information to interpret the results of the Michelson-Morley experiment. Discuss the role of the Michelson-Morley experiments in making determinations about competing theories**Common Misconception/Confusion:**What is the aether wind? Many students find this confusing, think about sticking your hand out the car window when it’s parked do you feel anything. Nope. What about when the car is moving? You feel the wind. This is basically the idea behind the aether wind. The Earth is moving through space so we should feel an Aether wind.**Why this video will help:**Neil deGrasse Tyson explains just what scientists thought before, and how Michelson and Morley changed scientific thinking forever. Click Here to Watch

**Syllabus Dot Point:**Discuss the principle of relativity**Common Misconception/Confusion:**You’ve probably read somewhere that the laws of physics are the same in all inertial frames of reference. What does that actually mean? What was Galileo’s idea of relativity?**Why this video will help:**This video goes over Galilean relativity with some examples of what we expect with Galilean transformations, and the idea of the laws of physics being the same in all inertial frames. Click Here to Watch

**Syllabus Dot Points:**Describe the significance of Einstein’s assumption of the constancy of the speed of light. Analyse and interpret some of Einstein’s thought experiment involving mirrors and trains and discuss the relationship between thought and reality. Identify that if c is constant then space and time become relative. Analyse information to discuss the relationship between theory and the evidence supporting it, using Einstein’s predictions based on relativity that were made many years before evidence was available to support it. Explain qualitatively and quantitatively the consequences of special relativity in relation to the relativity of simultaneity, the equivalence between mass and energy, length contraction, time dilation, and mass dilation.**Common Misconception/Confusion:**That’s a lot of dot points and I’ve chucked all of the main Special Relativity dot points together intentionally as they deserve to be attended to together. Many students find this whole section confusing. I put to you that if you stop for a moment and look at the concepts of Special Relativity itself, it’s actually a few simple rules.

It’s a bit like chess, watching the game from afar can look very complicated and the strategies are, but fundamentally there are only a few simple rules. Consider this scenario: You’re sitting on top of a car driving at 50 kph and you throw a ball off the roof at 10 kph. To an observer on the ground it looks like it’s going at 60 kph, all is well. If I do the same thing again but this time shine a torch. I see the light going at c, and you see it going at c as well, you don’t see c +50!

That is all special relativity says, the speed of light is constant everywhere. It’s actually a simple rule.

What are the consequences? How could it be that we both saw the light travelling at c, how is that possible! Well, in order to make light travel at c everywhere, lengths must contract and time and mass must dilate. Seriously stop and take that in. If I’m still and holding a metre ruler, and I ask you how long it is you’d say a meter. If I held that same ruler while running past you (admittedly I’d have to run pretty fast, do not try this at home), you’d no longer say it was a metre. Seriously, no joke, as far as you’re concerned that ruler has absolutely shrunk!

The results are indeed incredibly weird, but hopefully I’ve convinced you the rules that govern Special Relativity are actually pretty simple. Simple rules, bizarre results.

**Why these videos will help:**Click here to see a brief explanation of the origins of special relativity and general relativity. Click here to see a real world piece of evidence for time dilation, and then blow your mind with a bizarre thought experiment. This final video sums up the postulates of relativity and goes back to look at where the maths actually comes from, as you’ll see all you need is Pythagoras’ theorem: Click Here to Watch.

## Good Luck!

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**Vamsi Srinivasan** is looking to uncover the next hidden truth of the universe. He was so fascinated by the beauty of Physics and Mathematics during his HSC that he went on to study Physics at University. He is now in his second year of a dual degree in Physics/Computer Science. He loves physics and maths so much, he wanted to share his passion and has been an Art of Smart coach for the past 2 years. He’s helped coach students in physics as well as all ranges of HSC Maths from General to Extension 2. In his spare time you can find him watching Tennis or Formula 1 or perhaps listening to his favourite podcast ‘Hello Internet’.