I read on the US Environment Protection Agency website, that using a petrol lawn mower produces more carbon dioxide in an hour than a car produces whilst covering 300 miles. I had assumed that, when burning petrol, all of the carbon combines with oxygen in the air so the co2 produced varies in proportion to the amount of fuel burnt? What have I missed?

Simon Forbes

Hove

A few years ago I was fishing on a lough in Donegal. The water level had been raised by approximately 20cm by securing a plank of wood across the outflowing river. The area of the lough is about 10 km sq, so by my calculations the plank is holding back 2 million tonnes of water. But the plank isn't that strong, so how does it work?

I always assumed they were pinhole lenses, but then I realized I really don't know (and don't want to break apart a perfectly good phone).

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.

To stop battery chickens from feeling any pain or claustrophobia in their short lives would it be possible for scientists to genetically modify them to have no pain receptors, touch receptors, be blind and not be able to see. I know this sounds even worse in ethical terms but would it stop the sufferance of the chickens as they would not know what would be going on and would only know how to eat and lay numerous amounts of eggs.

Is there a tool used in formula 1 pitstops which allows the wheels to align properly like the machines in large garages? It seems that tyre wear would be reduced by a large amount if something like this was used.

If I place a block on a conveyer belt moving at 10m/s then place that conveyer belt on another conveyer belt moving at 10m/s in the same direction the block would now be moving at 20m/s. We are always told it is impossible to get things quicker than the speed of light but with enough conveyer belts moving at high enough speeds why would it not be possible to get the block moving this fast? All impracticallities aside