Veritasium
Does Pressure Melt Ice?
- Title
- Does Pressure Melt Ice?
- Date posted
- 15 years ago
- Description
- When pressure is applied to ice, its melting point is reduced so it turns to water. When the pressure is removed, however, it turns back into ice. This process is called 'regelation.' Big thanks to Art of Ice Sculptures www.icesculpture.com.au who donated the beautiful block of ice.
- Title
- Why Is Ice Slippery?
- Date posted
- 15 years ago
- Description
- In Sydney, ice melts because it is warm out in the middle of the day (even in winter). This creates a layer of water on top that certainly makes it slippery. But should it be slippery at night or in a cold northern climate where the air temperature is below zero? Yes, because the pressure your skates apply to the ice actually lowers its melting point allowing you to glide along a thin layer of water.
Animation in this video is courtesy of VisChem (TM), Copyright 1995, Roy Tasker
For a more complete picture of the mechanisms involved in making ice slippery, check out this great article: http://lptms.u-psud.fr/membres/trizac/Ens/L3FIP/Ice.pdf
- Title
- How Does The Earth Spin?
- Date posted
- 15 years ago
- Description
- One of the most common physics misconceptions is that an unbalanced force causes constant motion. In truth, an unbalanced force leads to changes in motion - accelerations.
- Title
- Why Does The Earth Spin?
- Date posted
- 15 years ago
- Description
- The Earth spins on its axis, completing a full revolution every day. By why does it do this? One of the most common misconceptions in physics is the belief that constant motion requires a constant force. So many people believe there must be some force in the Earth (e.g. gravity, centrifugal force) that keeps it spinning. In truth, no force is required because a fundamental property of mass is that it maintains its state of motion in the absence of external forces. This property is called inertia.
- Title
- Persistence Of Vision
- Date posted
- 15 years ago
- Description
- Everything is not as it first appears. This simple plastic ball looks purple until you swing it in a circle and reveal its true nature. Inside are three light emitting diodes (LEDs), which are red, green and blue. They turn on and off in sequence very quickly. When still, the ball appears purple because your eyes and brain don't 'refresh' quickly enough to perceive the changing colours. However, when swung in a circle, the ball changes colours at different locations so the colours don't merge with each other and the ball's true nature is revealed. Now let's not think too carefully about how this illusion is conveyed through video (because the camera doesn't refresh quickly enough to perceive the colours changing either - so you have no hope of seeing it on YouTube even frame by frame).
- Title
- Fire Syringe
- Date posted
- 15 years ago
- Description
- When air is compressed very quickly, it can reach high temperatures. In this demonstration we show how cotton wool can reach the point of auto-ignition by quick compression of air in the fire syringe.
- Title
- Misconceptions About Heat
- Date posted
- 15 years ago
- Description
- When we touch something that is hot or cold, what are we actually sensing? Is it the temperature of the object, or the rate at which heat flows between the object and our hand?
- Title
- Can You Solve This Shadow Illusion?
- Date posted
- 15 years ago
- Description
- When sunlight shines through a small hole, it casts a circular image on the wall regardless of the shape of the hole. The size of the hole also doesn't affect the size of the image.
This counterintuitive demonstration shows that the hole is acting like a pinhole camera, producing an image of the sun on the wall. Therefore the size and shape of the hole have no effect on the size and shape of the image.
- Title
- Can You Perceive Acceleration?
- Date posted
- 15 years ago
- Description
- How do our eyes scan across a landscape? Contrary to popular belief, they don't scan smoothly across a scene, they observe a series of images. The eye is capable of panning smoothly however. If something moves in your field of view, your eyes track it smoothly. This has an important effect on our perception of motion. It makes it more difficult to see when objects are accelerating since the eye tracks all motion quite smoothly.
- Title
- Option E - Acceleration of a Bungy Jump
- Date posted
- 15 years ago
- Description
- On the rebound, the acceleration varies. The jumper is accelerating up but as the bungy recoils, the jumper starts accelerating down again due to the pull of gravity. This does not mean that he's moving down, however, only that his velocity upwards is decreasing.
- Title
- Option D - Acceleration of a Bungy Jump
- Date posted
- 15 years ago
- Description
- Congratulations, the acceleration of the bungy jump is greatest at the jumper's lowest point. This is because the bungy is now stretched to its maximum, meaning if applies a force up on the jumper more than twice his weight. This means he accelerates up at a greater rate than the acceleration down when he left the platform.
- Title
- Option C - Acceleration of a Bungy Jump
- Date posted
- 15 years ago
- Description
- At the jumper's fastest point, the acceleration is by definition zero. That is because the jumper is going from speeding up to slowing down. At this instant then there is no change in the jumper's velocity. This is counter-intuitive for a lot of people because it's easy to confuse velocity with acceleration. Velocity is how fast something goes while acceleration is the rate at which velocity changes.
- Title
- Option B - Acceleration of a Bungy Jump
- Date posted
- 15 years ago
- Description
- When the rope becomes taut, the force on the jumper is mainly his weight downwards, plus a bit of air resistance up. Therefore his speed is increasing nearly as much as it did when he leapt off the platform. So this is not the greatest acceleration of the jump.
- Title
- Option A - Acceleration of a Bungy Jump
- Date posted
- 15 years ago
- Description
- Right after leaving the platform, the only significant force acting on the bungy jumper is his weight. This causes him to speed up from rest. His speed increases every second by nearly 10 m/s. This is not the maximum acceleration experienced by a bungy jumper, however.
- Title
- When Is A Bungee Jumper's Acceleration Max?
- Date posted
- 15 years ago
- Description
- When is the acceleration (rate of speeding up or slowing down) greatest during a bungy jump?
- Title
- Veritasium Bungee Jumps!
- Date posted
- 15 years ago
- Description
- In Queenstown, New Zealand, I jumped off the Kawarau Bridge - the site of the first bungy jump. It was a thrilling experience, preceded by a terrifying, gut-wrenching half hour wait. All in all an awesome adventure, even if the woman fitting my harness didn't know the first thing about the acceleration of free-falling bodies.
- Title
- Where Did The Earth Come From?
- Date posted
- 15 years ago
- Description
- Do we take the Earth for granted? It gives us life and sustains us in the manner we're accustomed to, but we don't know the first thing about it: like where did it come from? And how did it form? Most people recognize that the Earth has a big explosion in its history, which they refer to descriptively as the 'Big Bang.' But there are two very good reasons why the Big Bang is not directly responsible for forming the Earth: 1) It happened 13.7 billion years ago. That's more than 9 billion years before the Earth formed (what happened during that time?), and 2) After the Big Bang the universe consisted of only Hydrogen and Helium - not great raw material for building the Earth. The truth is the big bang formed stars, which exploded and then (perhaps) formed more stars, which exploded and then formed our solar system, including the Earth. The early stars performed the vital role of making the heavier elements of which Earth is composed and we are made.
- Title
- How Old Is The Earth?
- Date posted
- 15 years ago
- Description
- The Earth is clearly old, but exactly how old was difficult to work out. People long believed the Earth had only existed for several thousand years. Then, in the 1800's, a study of geological features (including fjords) led scientists to the conclusion that the planet must be much older - at least millions of years old. Later, the discovery of radioactivity provided a mechanism by which the Earth's core could be continually heated. This meant it was much older than previous estimates of 20-40 million years based on the cooling rate of the Earth. Today through many different methods we have established that the Earth is roughly 4.54 billion years old!
- Title
- What Is Electricity? (Are You Gonna Be My Girl?)
- Date posted
- 15 years ago
- Description
- 1, 2, 3 A song about 'lectricity
because it powers our lives
makes it possible for us to thrive
because it powers our lives
makes it possible for us to thrive
Oh, 4, 5, 6, volts of potential difference
makes electrons go round
if the circuit is complete and sound
Circuit's closed
Voltage There
Current Flows
Power Everywhere
We use AC,
in factories
and homes because we can transform it
High voltage
transmits with lower loss
but low voltage is best for safety
I said what is electricity?
Well, so 1,2,3 a song about 'lectricty
because it powers our lives
makes it possible for us to thrive
because it powers our lives
makes it possible for us to thrive
Oh, 4,5,6 volts of potential difference
makes electrons go round if the circuit is complete and sound
Heat makes steam
turns tu...
- Title
- Types of Radiation
- Date posted
- 15 years ago
- Description
- An introduction to alpha, beta, and gamma radiation
- Title
- Sound + Fire = Rubens' Tube
- Date posted
- 15 years ago
- Description
- Sound waves in a tube of gas create flames of different heights that dance to the music. A metal tube with holes in it is filled with gas. The gas is lit to create a row of tiny flames. A speaker at one end plays sound into the tube, which creates a standing wave of sound: areas where air molecules are vibrating rapidly separated by areas where the air is fairly still. This produces the different heights of flames and allows the wavelength of the sound wave to be estimated.
- Title
- Radiation vs Radioactive Atoms
- Date posted
- 15 years ago
- Description
- There seems to be confusion about what radiation is and where it comes from. Many people believe it is the radiation that comes directly from nuclear power plants that poses a threat to public safety. In fact it is the radioactive atoms, which can escape in the event of an explosion, that pose a safety risk. They can be scattered by the wind over hundreds of kilometres. Then they may be ingested or breathed in. If they release radiation at this point, it is damaging to the body's molecules and cells because the radiation is delivered directly to tissues.
- Title
- Galileo the Scientific Parrot
- Date posted
- 15 years ago
- Description
- On the surface of Earth all objects accelerate downwards at the same rate - at least, they're supposed to. But we all know dust, pieces of paper, and feathers fall slower. This is of course due to the influence of air resistance. In this experiment we use an evacuated cylinder to test whether a coin and feather really do accelerate at the same rate.
- Title
- What Powers Australia?
- Date posted
- 15 years ago
- Description
- Countries are powered by a diverse range of energy sources, but in Australia electricity generation mainly has one source: fossil fuels. Coal, natural gas, and oil account for over 90% of the country's electricity. Hydro provides 7% with only 0.3% provided by wind and solar. Should Australia consider nuclear power? It is a complicated issue leaving many uncertain about its place in Australia's energy future.
- Title
- How Damaging is Radiation?
- Date posted
- 15 years ago
- Description
- What is radiation? Are all types harmful? What are the most common sources of damaging radiation? Most people view radiation as harmful and negative without understanding what makes it potentially damaging and which forms should be avoided. For example, many felt radiation from mobile phones probably caused cancer but few focused on the carcinogenic effects of UV rays.
- Title
- Supercooled Water - Explained!
- Date posted
- 15 years ago
- Description
- Many videos on YouTube show water freezing almost instantaneously. This video shows you how to replicate the experiment and it explains how the phenomenon works. Molecular illustrations are courtesy of:
PhET Interactive Simulations
University of Colorado
http://phet.colorado.edu.
- Title
- What Are Atoms and Isotopes?
- Date posted
- 15 years ago
- Description
- Most people recognize that atoms are the fundamental building blocks of all matter around us. An atom itself is composed of protons, neutrons and electrons. The simplest atom is the hydrogen atom because it consists of only one proton and one electron. If a neutron is added to the nucleus, the atom is still hydrogen, just a more massive version. Atoms of the same element (i.e. those with the same number of protons) but different numbers of neutrons are called isotopes.
- Title
- Khan Academy and the Effectiveness of Science Videos
- Date posted
- 15 years ago
- Description
- My PhD: https://ve42.co/phd
It is a common view that "if only someone could break this down and explain it clearly enough, more students would understand." Khan Academy is a great example of this approach with its clear, concise videos on science. However it is debatable whether they really work. Research has shown that these types of videos may be positively received by students. They feel like they are learning and become more confident in their answers, but tests reveal they haven't learned anything. The apparent reason for the discrepancy is misconceptions. Students have existing ideas about scientific phenomena before viewing a video. If the video presents scientific concepts in a clear, well illustrated way, students believe they are learning but they do not engage with the media on a deep enough level to realize that what was is presented differs from their prior knowledge. There is hope, however. Presenting students' common misconceptions in a video alongside the scientif...
- Title
- Experiments A Cappella
- Date posted
- 15 years ago
- Description
- A short a cappella tribute to experimentalists. It is sung while performing three simple experiments with household items: Mentos dropped in diet Coke, a tea bag emptied and burned, and a ping pong ball floating in the air stream of a hair dryer.
- Title
- Three Incorrect Laws of Motion
- Date posted
- 15 years ago
- Description
- Newton's Three Laws of Motion are a landmark achievement in physics. They describe how all objects move. Unfortunately most people do not really understand Newton's Laws because they have pre-existing ideas about the way the world works. This film is about those pre-existing ideas. By recognizing what people are thinking, it becomes easier to describe the correct scientific concepts of Newton's Three Laws and how they differ from this 'intuitive physics'.
- Title
- Is There Gravity In Space?
- Date posted
- 15 years ago
- Description
- If you've seen footage from the International Space Station or any of the space shuttle missions, you know that astronauts float around as they orbit the Earth. Why is that? Is it because the gravitational force on them is zero in space? (Or nearly zero?) The truth is that the strength of the gravitational attraction is only slightly less than it is on Earth's surface. So how are they able to float? Well, they aren't floating - they're falling, along with the space station. They don't crash into the Earth because they have a huge orbital velocity. So as they accelerate towards the Earth, the Earth curves away beneath them and they never get any closer. Since the astronauts have the same acceleration as the space station, they feel weightless. It's like being in a free-falling elevator (without the disastrous landing).
Director of Photography: Stefan Smith
Camera Assistant: Raa Perajeev
Boom Operator: Maha Sivalingam
Production Coordinator: Adrian T...
- Title
- Misconceptions About Falling Objects
- Date posted
- 15 years ago
- Description
- If you drop a heavy object and a light object simultaneously, which one will reach the ground first? A lot of people will say the heavy object, but what about those who know both will land at the same time? What do they think? Some believe both objects have the same gravitational pull on them and/or both fall to the ground with the same constant speed. Neither of these things is true, however. The force is greater on the heavy object and both objects accelerate at the same rate as they approach the earth, i.e. they both speed up but at the same rate.
- Title
- Which Hits The Ground First?
- Date posted
- 15 years ago
- Description
- A basketball and a 5kg medicine ball are dropped simultaneously. Which one hits the ground first? It seems obvious that the heavy one should accelerate at a greater rate and therefore land first because the force pulling it down is greater. But this is forgetting inertia - the tendency of mass to resist changes in motion. Therefore, although the force on the medicine ball is greater, it takes this larger force to accelerate the ball at the same rate as the basketball.
- Title
- Calculating Gravitational Attraction
- Date posted
- 15 years ago
- Description
- Newton's Law of Universal Gravitation can be summarized as "all mass attracts all other mass." But if this is true, why don't we notice the gravitational force of attraction between everyday objects? The reason is because the gravitational force is quite weak.
- Title
- Best Film on Newton's Third Law. Ever.
- Date posted
- 15 years ago
- Description
- There is a gravitational force of attraction between the Earth and the moon, but is it mutual? That is, are the forces on the Earth and the moon equal? Most people would say no, the Earth exerts a greater force of attraction because it is larger and has more mass. This is a situation in which Newton's Third Law is relevant. Newton's Third Law says that for every force, there is an equal and opposite reaction force. So the force the Earth exerts on the moon must be exactly equal and opposite the force the moon exerts on the Earth. But how can that be - that the same size force keeps the moon orbiting, but barely affects the Earth? The answer is inertia - the tendency for all objects with mass to maintain their state of motion. Since the Earth has much more mass than the moon, it has greater inertia and therefore experiences much less acceleration for the same amount of force.
- Title
- What Is Gravity?
- Date posted
- 15 years ago
- Description
- People have a lot of different ideas about what gravity is: a downward force that stops you from flying off into space, an attraction smaller objects experience towards larger objects, or a mutual attraction between all masses. It is the last of these ideas that best reflects a scientific conception of gravity.
- Title
- Why Does the Moon Orbit Earth?
- Date posted
- 15 years ago
- Description
- It takes the moon about 27 days to orbit the Earth. What makes it go round? It is the gravitational attraction of the Earth on the moon. Due to the moon's velocity, the Earth keeps pulling the moon towards it without the moon actually getting closer to the Earth. This is similar to how satellites orbit the Earth.
- Title
- What Forces Are Acting On You?
- Date posted
- 15 years ago
- Description
- What forces (i.e. pushes or pulls) are acting on you right now? Most people can identify the gravitational force down, but there must be something else otherwise you would accelerate down towards the center of the Earth. The other main force on you is called the normal force. It is a force perpendicular to the surface that supports you, like the ground or the seat of your chair. You compress this surface and it acts like a spring, pushing you up.
- Title
- What is a Force?
- Date posted
- 15 years ago
- Description
- Force is a central concept in physics. By analysing the forces on an object, its resulting motion can be determined. But what exactly is a force? The word force is used in everyday language in a variety of contexts, only some of which reflect the scientific definition of force. In this video, people at Victoria Park in Sydney are interviewed on their ideas of force and the forces that act on them.
- Title
- How Far Away is the Moon? (The Scale of the Universe)
- Date posted
- 15 years ago
- Description
- If the Earth were the size of a basketball and the moon a tennis ball, how far apart would they be? Diagrams that are not to scale make us think that they're closer than they really are.
- Title
- Gravity (Scientific Version of John Mayer's Gravity)
- Date posted
- 15 years ago
- Description
- A song about Gravity set to the tune of John Mayer's Gravity.
Gravity is working with me
And Gravity, keeps me on the ground
All mass attracts all other mass
a force proportional to mass one and two
and inversely to the distance between them squared
Oh, gravity is working with me
and gravity, makes apples fall to ground
Oh twice the mass has twice the pull
but the force on each is still equal
It keeps the moon and the satellites
going round
Oh twice the mass has twice the pull
but the force on each is still equal
It keeps the moon and the satellites
going round
Oh gravity, the force that makes weight on me
Woah, gravity, now general relativity (how can that be?)
The force between us all is
The force between us all is
The force between us all is
Gravity between us all is
Gravity between us all is
Gravit...
- Title
- Egg Experiment to Demonstrate Inertia
- Date posted
- 15 years ago
- Description
- If you spin a raw egg and then stop it, it will start spinning again without you having to touch it. A boiled egg, on the other hand, stops and stays stopped. Why is this? Well a raw egg contains a yolk that moves inside the egg independently of the shell. If you stop the shell, the yolk inside continues to move due to its inertia and it therefore gets the egg spinning again.
- Title
- The Difference Between Mass and Weight
- Date posted
- 15 years ago
- Description
- There is a common perception that weight and mass are basically the same thing. This video aims to tease out the difference between mass and weight by asking people what makes a car difficult to push. The standard answer is that it is difficult to push because it's heavy. But heaviness is a measure of weight, the gravitational pull of the Earth attracting the car to Earth's center. When the car is pushed on a flat road, the force of gravity does not oppose the motion. Instead the resistance felt is an indication of the car's mass which determines its inertia. Inertia is the property of matter that means it tends to resist acceleration - the greater the mass, the less the acceleration for a given amount of force.
- Title
- Scientific Notation - Example
- Date posted
- 15 years ago
- Description
- If the sun were entirely made of protons, how many would there be in the sun? How can this be worked out using the Google search field?
- Title
- I'm Atoms (Scientific Cover of Jason Mraz's I'm Yours)
- Date posted
- 15 years ago
- Description
- Well an atom's made of protons, neutrons, and electrons
the first two in the nucleus, the third around it
it's mostly empty space, but it feels solid in any case
The elements are all the different types of atoms
they differ by the number of protons in the middle.
Hydrogen has only one, but Uranium has a ton
It's just chemistry that you and me are made of these atoms
Well atoms bond together to form molecules
Most of what's surrounding me and you
Water, sugar, things yet undreamed of of of of
Look around you, see the combinations in a eucalypt tree
Mendeleev's periodicity
gives us sand and water and the air above ove ove ove ove
It's just chemistry that you and me are made of these atoms:
Hydrogen, Oxygen, Carbon, Nitrogen, make up the world's life forms
Do do do you, do do do do
but do you wonder how
matter forms somethi...
- Title
- Scientific Notation - Explained!
- Date posted
- 15 years ago
- Description
- Scientists have to work with some very large and some very small numbers. To represent these numbers more easily, they use scientific notation. Scientific notation relies on powers of 10. This video gives examples of how to represent a large and small number and explains powers of ten.
- Title
- Cathode Rays Lead to Thomson's Model of the Atom
- Date posted
- 15 years ago
- Description
- In the mid 1800's scientists successfully passed an electric current through a vacuum in a glass tube. They saw a glow from the tube that seemed to emanate from the negatively charged plate called the cathode. Since scientists didn't know what the glow was they called it a cathode ray. There was debate over whether the cathode ray was a wave phenomenon like light or a stream of negatively charged particles. JJ Thomson effectively resolved the debate in 1897 by performing a clever experiment that determined the charge to mass ratio of the particles making up the cathode ray. He also showed that this same particle was in all different cathode materials so it must be a constituent common to all atoms. This changed our understanding of the atom from the previous billiard ball model to Thomson's plum pudding model of the atom.
- Title
- Thomson's Plum Pudding Model of the Atom
- Date posted
- 16 years ago
- Description
- JJ Thomson proposed the first model of the atom with subatomic structure. He had performed a series of experiments and was credited with the discovery of the first sub-atomic particle, the electron. He therefore proposed a new model of the atom called the plum pudding model. In this model, the plums represent negatively charged electrons which can be plucked out of the atom, leaving behind some positively charged pudding. In this film, cherry tart is used as a delicious substitute for plum pudding.
- Title
- Atomic Theory
- Date posted
- 16 years ago
- Description
- This is the first Veritasium science video. It addresses one of the most fundamental concepts in science: the idea that all things are made of atoms, tiny particles that are in perpetual motion. They attract each other when a little distance apart and repel when squeezed together.
- Title
- What causes the seasons?
- Date posted
- 16 years ago
- Description
- There are a few persistent misconceptions about what causes the seasons. Most believe it is the distance between the Earth and sun which varies to give us seasonal temperature variations. However it is actually the directness of the sun's rays leading to more intense sunshine in summer and less in winter.
