It's a popular cliché to say that you wait ages for a bus, and then three turn up at once. But is there any truth to this? Or is it a false impression formed because we notice coincidences more than other events?

If true, are there laws governing this behaviour, and are there any natural phenomena that obeythe same principles?

Clare Redstone, London, UK

If you sink an object and then let go then it accelerates upwards. What if I sank something a very long way (say a mile or so)?

I've read in New Scientist about the potential of using supercavitation to travel very fast through water.

So what’s to stop me attaching a lightweight projectile onto a big rock with a piece of string which will detach at a certain depth, dropping it off a boat and firing something into space?

Some engines can operate at higher temperatures/pressures than the human body. On the other hand, vehicles have extra weight, possibly have different drag characteristics, etc. For "normal" speeds and loads, what would be the properties of a vehicle at a crossover point equal to the efficiency of an average human?

When I was a child our school took us to the Physics Exhibition. I saw a bell in a case was ringing. The supervisor made inside the case vaccum and the noise cut off.

Now I am studying mechanical Engineering, I have this question why manufacturers don't do something like that. I know it will make some problems. For instance, the heat transfer will be more challenge. But aren't they solvable?

They can put nosie damper after outlets and before inlets.

I'm sorry about my English.

This has been on my mind for some time but I couldn't think of a good cover story so I put off asking.  There is none, I am not writing a James Bond novel &c. I just have a morbid imagination and need help with the maths. 

So if a person, A, (James Bond, Chumpington Bleakly, whoever) were to make a parachute jump from an aeroplane with a noose around his neck connected to B, (an anvil) which is also pushed from said aeroplane I'm thinking that (forgive my limited understanding of things if this is wrong) B's terminal velocity is going to be greater than A's and a force will be exerted on A's neck.  Would the force be great enough to invertihang A before the descent is complete without recourse to the parachute?

How fast would a formula one car need to go to drive upside down for a period of time and could it actually be done?

Why are car horns located in different places on US cars vs. European and Japanese cards.  I was driving my wifes car and got into a situation where I needed to use my horn.  I instinctively went for the center of the steering wheel but on her car the horn was located in the top right of the steering wheel center area.   By the time I found the horn it was too late to toot!   Given this is something that needs to be found quickly in an emergency why is there not a standard for this in the USA?

If all road vehicles were electric, I'd like to know how much electrical power would be consumed ( and how many more power stations would be needed ) to keep things running at more or less the same levels of traffic as today. . .

It is very distinctive and seems unchanged over decades and brands, but does it come from paint, plastic or something else? And if so, why is it the same across all cars? Or have the manufacturers bottled a fragrance which they secretly spray to seduce new car buyers?

William Coley, London, UK