Scientists have recently discovered nanodiamonds in the flames of ordinary candles. They are produced at a rate of about 1.5 million per second. Unfortunately they are also burned up at this rate and released into the atmosphere as carbon dioxide. Still this finding may prove useful in the ongoing search for economical ways to produce diamonds.
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 http://www.icesculpture.com.au who donated the beautiful block of ice.
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
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.
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.
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).
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?
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.
When is the acceleration (rate of speeding up or slowing down) greatest during a bungy jump?
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.