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10

In a sense, wax does not burn, at least not in the same way that, for instance, magnesium burns. Instead wax gets hot and vaporizes, and the vaporized wax is what burns. The heat of combustion vaporizes more wax, and the process continues. A candle wick works by forming a conduit for the pool of melted wax which forms around the base of the exposed wick. ...


7

As mentioned in the comments, this is an instance of supercooling. When you cool a liquid below its freezing point, the molecules are still moving around quite a lot and any two that stick together are likely to be broken up by a subsequent impact. Liquids freeze better when the molecules have something to latch onto -- either a block of the same ice they ...


5

Let's take this in steps. First - assume there is zero friction between the bottom block and the tower, and between the bottom block and the ground. If I move the block "infinitely quickly" the tower will have had no time to tilt at all, and it will drop vertically (and remain upright). This tells me there are two things to consider: the time take to ...


4

Curved roads are banked so that less transverse traction is required to prevent a vehicle from slipping. In some parts of the US (and perhaps elsewhere), there are "advisory" speed limit markings near tight turns, which are loosely related to safe speed allowed by the banking of the turn. Here's an example where the "ramp" limit is lower than the highway ...


4

Very roughly speaking, the danger to a living being riding in a crashing car is that of forces that arise within living tissues when that being is forced to change direction swiftly (being bumped in a sideswipe) or to stop suddenly. Those forces tear and injure living tissue. The physics and biophysics content of speedlimits is of setting states of motion on ...


3

If you or one of your friends has transition lenses for their glasses, then you can test the UV blocking ability with those. The transition to darker shades in these lenses is initiated by UV-light. So hold your sunglasses over some transition lenses and see if they start to turn darker. You can try this with any photochromatic material really, but ...


3

The glue used on plastic bottles is usually based on polyisobutylene or something similar to it. This has long hydrocarbon chains in it, and when the material is at equilibrium the polymer chains form a tangled network much like a mass of tangled wool. If you quickly stretch the polyisobutylene then the chains cannot untangle themselves because the ...


2

The lower speed limits are mainly determined by how fast a car needs to be able to stop. In town there are lots of children around, and you need to be able to stop quickly if a child runs into the road, so the speed limit in towns is low (30 mph in the UK). Where the risk is especially high, e.g. near schools, it's not uncommon for the speed limit to be ...


1

I tested it against a control and it worked. Used longneck glass bottles. Didn't measure the difference but the difference was notable to the touch after half an hour.


1

When you move with a certain velocity, you possess what is known as inertia of motion which is the measure of the difficulty to avert the motion. Since you have velocity, you have an associated momentum. Now, when your foot gets struck to the stone, by Newton's third law, the stone exerts a reactive force due to its deformation by the force applied by you. ...


1

If you think of the runner as being stationary and the ground as being the thing that moved, you can think of a rock hitting a rigid object off center. A torque is imposed on the body based on the force perpendicular to the body and the distance from it's axis of rotation.


1

Let's solve this in two parts. First, I will calculate how fast you need to go at the bottom of the swing in order to be able to make a complete loop (without the rope going slack). Next, I will estimate whether you can achieve this speed by "pumping" - that is, moving your center of gravity around to increase your speed. Part 1: speed needed The velocity ...


1

When plastic bottles are made they start with something that looks like a test tube with the threaded top for the bottle cap. It's heated and air is blown into it while it sits in a bottle shaped mold. Then it's quickly cooled to lock the plastic into that shape. The stretching creates residual stress in the plastic. It wants to un-stretch like a taught ...


1

Without knowing a lot more about the details of the entire system, we can't say exactly what the difference will be between the AC1+AC2 case and the AC2-only case. However, there are a few things we can work out from simple energy balance. In the following, I'm considering the air as an ideal gas with a fixed specific heat capacity at constant pressure ...



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