What determines whether a flat stone thrown at a water surface will skip, and what throwing angle gives the most bounces?
Physics
Post a problemWhy do clear droplets or 'legs' of liquid form and slide down the inside of a wine glass above the surface of the wine?
Does the direction a draining bathtub or sink swirls depend on hemisphere (Coriolis force), as commonly claimed?
Why does a falling flat card or leaf sometimes flutter side to side, sometimes tumble end over end, and sometimes fall steadily, depending on its shape?
Why does a flag (or any flexible sheet) in a steady wind start to flap periodically instead of staying still or moving smoothly?
Why do larger particles rise to the top of a shaken container of mixed granular material even when they are the same density or denser than the small particles?
What determines the characteristic drooping, fanned-out shape of a bundle of hair such as a ponytail?
How much water is needed to make wet sand cohesive enough to build a stable sandcastle, and why does too much or too little water make it collapse?
Why does a dry rod of spaghetti bent until it snaps almost always fragment into three or more pieces instead of two?
What causes a popcorn kernel to suddenly jump into the air at the moment it pops, and at what temperature?
Why does dead wood in humid winter forests sometimes sprout delicate silky threads of 'hair ice'?
What part of a whip actually produces the crack sound, and is it really breaking the sound barrier?
What inside a finger joint produces the popping sound when you crack your knuckles?
Is it true that centuries-old stained-glass windows are thicker at the bottom because glass is secretly a slowly flowing liquid?
Why does peeling adhesive tape (or scratching certain crystals) sometimes give off flashes of light, and can it really generate X-rays?
Why does a hard-boiled egg spun fast enough on a table rise up and spin on its end?
Why does a spun coin or disk settling flat on a table spin faster and faster, with the clatter rising in pitch, right up to the instant it stops?
Why does a rattleback (celt) toy spin smoothly in one direction but wobble and reverse its spin when started the other way?
Why does a spun tippe top (a truncated-sphere spinning toy) flip over and spin balanced on its stem instead of its round base?
Is it really true that dropped buttered toast is more likely to land butter-side down, and if so why?