Wagon wheel effect

While my son was playing with his Legos, he came up with an interesting question. I had thought about this when I was a kid, but never was inquisitive enough to look for an answer. My husband felt the same. We all get occupied with the demands of our education system that we forget to look into the life around us.

The question was" when I rotate this wheel fast, it appears to rotate backwards.Why does it feel so? "

https://www.youtube.com/watch?v=fUoLpcjwgJc

 The answer is quite interesting, It's a beautiful optical illusion. When the wheel rotates at a high speed, there is a mismatch between the image sent and the image processed from our brain. Because of this mismatch, the optical illusion of wheel rotating backward takes place. This phenomenon is called 'Wagon wheel effect'.

Thanks to my son for letting us explore and learn new things. Thanks to Bala anna and Deepak Seshadri for giving additional ideas to explore. 

We observed the optical illusion is minimal or at times there is no illusion at all when there are no grooves on the wheel. We can observe this illusion in our car wheels too.

https://commons.wikimedia.org/wiki/File:The_wagon-wheel_effect.ogv

The wagon-wheel effect (alternatively, stagecoach-wheel effect, stroboscopic effect) is an optical illusion in which a spoked wheel appears to rotate differently from its true rotation. The wheel can appear to rotate more slowly than the true rotation, it can appear stationary, or it can appear to rotate in the opposite direction from the true rotation. This last form of the effect is sometimes called the reverse rotation effect. 

https://en.wikipedia.org/wiki/Wagon-wheel_effect#/media/File:WagonWheelEffect.gif

Roller Coaster

His dream is to build a roller coaster inside the house to move from one room to another :-) . For now using the available materials he built a small roller coaster. This design took nearly half a day for him to complete it successfully. Allowing them to do mistakes helps them to find better solutions for their problems.
https://www.youtube.com/watch?v=5I-PkswmsvA

Cole's fighter jet

He created a fighter jet with a shooting technique for his Cole Ninjago.
He took nearly 1.5 hours to complete this design. His aim was to shoot 2 bullets simultaneously with one single rotational force.
https://www.youtube.com/watch?v=oN6dSVHYcB0

Racing Car

Boys are crazy about cars.Here is the booster racing car which uses boosters for high power (As per my son's imagination).
https://www.youtube.com/watch?v=-fjSf0f1xpw

Is it ICE train or cargo train?

It's long since I updated my blog, but his passion towards creating things doesn't stop. He converted high speed train into a cargo carrier. The oil tankers are rotatable. He used some simple rotating mechanism.
https://youtu.be/76DArsb2g5I

https://www.youtube.com/watch?v=wapaU-BllE4

Kids love free time. Free play kindles their creative power to think differently and be themselves.

Have you ever tried walking backwards up the hill?

My 8-year-old curious son walked backwards quickly while climbing up the slope and asked us why is it easier to walk backwards in uphill than walking forward. We experimented and felt easier to climb. Why is it walking backward in uphill easier?

We got an amazing answer from Quora experts.

It can feel easier because of how weight and balance are distributed in the human body, and how our bones and muscles are structured make us better suited for walking forwards.  Our legs are designed for power more than ease of motion, so walking up a slope forwards can be more tiring or slower if we do so in a way that relies on our strength instead of a more efficient alignment.

Walking up a slope backwards is more similar to falling than climbing, due to how our weight is distributed across movements and the much different use of our knees and involved muscles.  But, if you walk up a slope backwards for a fair distance, you might notice that your muscles fatigue in a different way---a way that makes your legs feel a little shakier than muscle fatigue from forward walking.  Perhaps walking uphill backwards fairly often would strengthen those muscles, but we are constructed to excel more at forwards bipedal ambulation than other directions (so the natural size and location of muscle groups will always favor walking forwards overall).

We evolved from animals that were often utilizing locomotion more resembling crawling or other four-legged means of moving about, and retain some of that technique in our upright walking.  When some scientists were asked what a longer-lived and more efficient humanoid form might look like, outside the bounds of a particular evolutionary path, they suggested that backwards knees would entail less stress and wear over time.

So, your question pertains both to the physics of moving your body and also the evolutionary source of our traits as humans.  I did these same experiments as a kid.

What if Earth stops spinning?

Our son recently asked us 'What happens when the earth stops spinning?' Here is a beautiful video which explains in detail.Thanks to his teacher who recommended this you tube channel. Vsauce answers many of our 'whys'.

https://www.youtube.com/watch?v=K0-GxoJ_Pcg