Greenhouse gases are the chemical compounds within the earth's atmosphere which contribute to the greenhouse effect and global warming.

The most significant greenhouse gases are:

  • Water vapour (H2O)
  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Ozone (O3)

Other greenhouse gases include flourinated carbon compounds such as CFCs, carbon monoxide (CO), nitrous oxide (N2O) - and many others.


In motor racing grid is a term which can mean either the group of cars competing in a race and or the area just behind the start/finish line where the cars are positioned, using markings painted on the track surface, ready for the start. Grid position is often dictated by performance in qualifying, with the fastest driver/car combination taking pole position. In some race series other factors such as performance in previous races is used to determine the grid positions.

Outside motor racing, grid refers to the mains electricity supply network, which in the UK is called the National Grid. So 'grid electricity' means electricity from mains supply, rather than electricity from a vehicle's on-board battery.

GDI Gasoline direct injection

GHG Greenhouse gas

GM General Motors

GPS Global Positioning System

Porsche 911 cornering

In automotive use, g is most commonly used as a measure of lateral acceleration, ie cornering. It can also be used as a measure of acceleration in any other direction.

An acceleration of 1g is equivalent to the acceleration due to gravity, which is 9.81m/s2 (32ft/s2). If you drop an object, after one second it will be travelling at 9.81m/s, after two seconds twice that and so on (ignoring air resistance). That is an acceleration of 1g. An acceleration of 2g is twice as much.

The best road cars can generate 1g or more in cornering, braking and forward acceleration. F1 cars corner and brake at up to 6g, while an aerobatic or fighter pilot could experience up to 12g in tight turns.

By contrast, the average road driver rarely exceeds 0.2g in any direction.

A Gurney flap is a small upright fence added at the top of the trailing edge of a wing. It increases downforce at the expense of an increase in drag.

The Gurney flap was introduced in US single-seater racing in the early 1970s by driver/engineer Dan Gurney.