In theory you are correct - there is more potential power available in a decent set of rim brakes than a hub mounted disc brake due to the longer braking track providing more friction and more mass for cooling.

This is why Maguras hydraulic rim brakes were so popular in the late 90's and early 2000's - disc brake technology hasn't really matured at that point, and hydraulic rim brakes gave advantages in modulation and power over cable actuated v brakes.

I more recent years mountain bikes have switched over almost entirely to disc brakes (either cable or hydraulic), and road cycling is starting to convert because while rim brakes have some advantages in theory, in practise these advantages are very small and unnecessary, and the hub mounted disc format provides some other big benefits.

In terms of raw power, it just isn't necessary in most cases. Even a fairly basic v type cable rim brake can lock a wheel completely solid with little effort, so what we are looking for is modulation and control - the ability to fine tune how hard the brakes are applied, which hydraulic systems give better control over (as the fluids won't compress as you pull the lever, while cables can stretch).

Looking at the components themselves, a solid disc means the pads push against something completely solid and incompressible, while a wheel rim means they are pushing against a hollow section which can flex under pressure. Similarly the disc brakes caliper is one solid piece, while a rim brake has arms mounted to opposing fork legs or seat stays which have some ability to flex.

And then there are the big practical benefits that are nothing to do with stopping power - moving the disc away from the rim gives you far, far greater mud clearance, and stops your brakes becoming useless after one muddy puddle. The same also means that slight damage to a rim will no longer jam a brake (and the brake is much better protected from damage itself). Separately you also gain the ability to design rims without any need for a braking track - so mountain bike rims can be made stronger, and road rims can be made more aerodynamic, and without any worry or concern over having to form a braking track in carbon fibre (which generally sucks).

So while there are some theoretical benefits to run brakes, they are vastly offset by the very real benefits of discs in most use cases. They have all of the power and modulation we need (noting that a lot of riders even use smaller 160-180mm rotors over the 200mm+ of the big gravity riders), with other benefits thrown in.

Place something underwater, and the pressure of the water all around it will try to push the water in to any small gaps or spaces in the casing.

Depth is important because the deeper underwater you are, the greater the pressure you experience will be - so the deeper you go the harder the water is trying to be pushed into the device.

Time matters because once you reach a pressure where fluid can leak in, this still takes a while to happen. If your gasket is 1mm thick, and the water will be able to push through that seal at a speed of 0.1mm/minute, then your device will stay dry for up to ten minutes, but after that point the water will potentially have compromised it.

So when manufacturers test a device, they choose a pressure and time to test for and to rate the device as.

Sounds can be drawn as a wave, so for one of the simplest examples let's look at a sine wave - just a simple, regular wave shape.

As a simple maths experiment, if we mirror this wave around the horizontal axis so that where one wave goes up, the other wave goes down, and then add them together, they will cancel each other out.

This works with sound in headphones too. If we stick a little microphone on the outside of your headphones so that it detects the outside sound you will hear, then takes that sound and inverts it so it is upside down and plays that through your headphones, the two will cancel out and the outside sound will vanish. If you play the inverted sound alongside the music or other audio you actually want to hear, you get both at the same time - no outside sound, just the extra audio you are adding.

Incidentally, this works really well with headphones, because the microphone can easily detect exactly what your ear will. If you tried this with a whole room, the way sound reflects off of surfaces will mean that the 'noise' sound will be different depending on exactly where you stand, so it is impossible to cancel it out - you could set it up to cancel nicely in one place, but if you moved about in the room in other places it won't work at all, or may make the noise worse.