Tag Archives: physics

Science Explained: Wind Powered Vehicle Traveling Faster Than the Wind

This is an interesting explanation of a the physics involved with vehicle propulsion. And it is a great video showing the scientific method at work.

They only touch on it a little bit but the need for creating 4 versions of the small treadmill device to illustrate the principles in action is a great example of how science inquiry and engineering work. There are often many failed attempts before an engineering solution to the issue involved can be properly created (video on Xyla Foxlin’s efforts: Building the Vehicle Physicists Called Impossible).

Enjoy the videos.

Veritasium is also offering 3 prizes to split the $10,000 for 1 minute videos that highlight science communicators with his Veritasium Science Communication Contest.

Related: The Amazing Reality of Genes and The History of Scientific InquiryScience Explained: Momentum For String of Metal BeadsCircumhorizontal Arcs – Fire Rainbows – Cloud RainbowsScientific Inquiry Leads to Using Fluoride for Healthy Teeth

The Feynman Lectures on Physics Available Online

The Feynman Lectures on Physics are now available to read online. They are a great collection of lectures covering physics and touching on many areas including: the Mechanisms of Seeing, Semiconductors and Algebra. This is a fantastic resource for learning about physics.

You can also get a boxed set of The Feynman Lectures on Physics for those that like paper. It is fantastic but not cheap.

Bill Gates bought the rights to the rights to The Character of Physical Law, 7 lectures Feynman gave at Cornell University (these are separate from the lectures listed above) and made them available online, which is great. Unfortunately the website is based on Microsoft tools and therefore quite a bother for many (or maybe even impossible with Linux computers – I am not sure). I guess since he made all his money via Microsoft it isn’t that surprising but it would have been nice if he provide the content in a more easily accessible way (even if they didn’t do the fancy additions they did on the Microsoft site. These are great enough videos to probably be worth the bother of installing proprietary Microsoft software in order to view them.

Related: Video of Young Richard Feynman Talking About Scientific ThinkingFeynman “is a second Dirac, only this time human” (Oppenheimer) – Classic Feynman: All the Adventures of a Curious Character

How Do You Lose Weight While You Sleep?

In this interesting webcast, Derek Muller, (a physics teacher in Perth, Australia) explores how much weight you lose while you sleep. As physics teacher he asks the sensible question: how do you lose weight while you sleep, what weight do you lose?

His conclusion is you lose weight through perspiration, water vapor in your breath and expelling carbon dioxide. Losing the water weight is pretty straight forward. The process of adding carbon to the breath we expel is not something I thought of. He calculates that we lose about 100 grams of carbon during a night of sleep. In his somewhat scientific experiment (measuring himself for several days) he lost about 150 more grams, which he attributes to water vapor and perspiration.

It seems to me the amount of carbon we lose during sleep is probably much more consistent than the amount of water weight we lose (both between people and variation between different days).

Related: Can You Effectively Burn Calories by Drinking Cold Water?CDC Urges Reducing the Amount of Salt We EatWhy is it Colder at Higher Elevations?How Caffeine Affects Your BodyWhy Does the Moon Appear Larger on the Horizon?

How to Walk on Ice

infographic explaining how to walk on ice - walk like a penguin

Infographic by Tablet. Falling on ice leads to many injuries and even 60 deaths a year in the USA (about the number that will die due to tornados). The graphic encourages thinking like a penguin. Penguins walk well on ice (in some ways) and they also fall well.

Seeking to keep your weight well supported (short strides) is wise (and sliding instead of picking up your feet can help). Falling well is also important. It is basic physics, you want to lower your center of gravity if you are start to slip and avoid any excessive force (so sliding is better than trying to stick out your hand and support all your weight). The elderly are especially susceptible to injuries – avoiding taking direct shocks to the wrist, knees or hips is wise). It does seem kind of silly to learn how to fall but it is very helpful in avoiding injuries.

On sidewalks if you are going to fall and there is snow piled up off the sidewalk, falling into the pile of snow may well be softer than falling directly onto the sidewalk.

On ice you have lower friction so strategies that require friction are not useful – quick moves often rely on very sturdy bases (which are based on the friction of our shoe on for example concrete [which normally is good – though business shoes are not very good] and on ice [where it is very poor – sliding and gradual moves are better]).

Related: Falling SafelyMinistry of Silly WalksMake Crosswalks More VisibleWhy Wasn’t the Earth Covered in Ice 4 Billion Years Ago – When the Sun was DimmerScience Toys You Can Make With Your Kids

Circumhorizontal Arcs – Fire Rainbows – Cloud Rainbows

photo of rainbow in a cloud

Fire Rainbow, Johor Bahru by John Hunter

Yesterday afternoon I spotted this odd, colorful, spectrum seemingly in a cloud in Johor Bahru, Malaysia. The colors are similar to a rainbow but the prism effect takes on a bit different form than a rainbow as I learned with a bit of searching online. I added a short post to this blog, about the phenomenon a few years ago.

photo of a large cloud over Johor Bahru

Johor Bahru under a large cloud which is topped with a fire rainbow.

A circumhorizontal arc is an optical phenomenon – an ice-halo formed by plate-shaped ice crystals in high level cirrus clouds. They are also known as “fire rainbows,” if the cloud is at the right angle to the sun, the crystals will refract the sunlight just as when rainbow is created.

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Why is the Sky Dark at Night?

The answer isn’t quite as simple as it seems. I find the wording in the video a bit confusing.

The point I believe, is that the sky is dark instead of light. But not that the brightness would be huge (so for example, you couldn’t necessarily read my book outside just by starlight). The light would be very faint, it is just that it would be lightish instead of blackish, due to the reasons explained (redshift etc.). At least that is my understanding.

Related: Why is it Colder at Higher Elevations?Why Does the Moon Appear Larger on the Horizon?Why is the Sky Blue?Why Wasn’t the Earth Covered in Ice 4 Billion Years Ago – When the Sun was Dimmer

The Science Behind Hummingbird Flight

Aerodynamics of the hovering hummingbird

Hummingbirds and insects have evolved for sustained hovering flight from vastly different ancestral directions, and their distinct phylogenies underlie the differences in their aerodynamic styles. In all other birds—and, presumably, hummingbird ancestors—the downstroke provides 100% of weight support during slow flight and hovering. Given that many birds possess the mass-specific power (using anaerobic metabolism) to hover for short periods, the selective pressure on hummingbird ancestors was probably for increased efficiency (resulting in stiff wings with greatly simplified
kinematics), and an upstroke muscle (the supracoracoideus) that makes the recovery stroke rapid, while contributing enough to the hovering power requirements to allow the downstroke muscle (the pectoralis) to operate within its aerobic limits.

In other words, this pseudosymmetrical wingbeat cycle is good enough, and although hummingbirds do not exhibit the elegant aerodynamic symmetry of insects, natural selection rewards ‘good enough’ as richly as it does our aesthetic ideals

Related: Praying Mantis Attacks HummingbirdFriday Fun: Crow Sledding, Flying Back Up and Sledding Down AgainBird Using Bait to Fish