Ballast
Ballast is a F1 specific tuning option. Ballast allows you to add weight to an already light car, with the specific intention of altering the weight distribution of the car. This works hand in hand with Weight Balance. Modern F1 car have ballast of more then 150 Kg. Applying very expensive and very heavy metal ballast in precise places, usually but not always on the underside of the monocoque, on the as lowest place as possible to further lower the center of gravity.
For example, on the last race of 2008, after David Coultard crush, it became clear that RedBull Racing team is using small wolfram/tungsten plates strategically placed on endplates of front wing. As on most cars, the RB4 has tiny blocks of wolfram/tungsten inside the wing's main profile, hidden from view within covered housings. But in addition to this 'standard' ballast placing, the RB4's endplates also have detachable aerodynamically shaped covers which hide extra ballast pieces (small picture inset). The ballast may look small, but the high density of the ballast metal means they can carry 5 to 7 kilograms. This allows the weight distribution of the car to be moved more forwards, improving its overall weight distribution.
In a complete season, a team may use ten sets of these plates, at a cost over the year of something like a half million dollars and more. Most often teams use tungsten, but some resources talk about Osmium, Iridium, Platinum, and Rhenium, very expensive, rare, but very dens materials.
Just to highlight how dense Tungsten is:
Density Tungsten: 19.35g/cm3
Density Lead: 11.35g/cm3
Say the chassis of an F1 car without ballast - with driver weighs 450kg.
So we need to make up 200kg up in ballast.
With Tungsten, that takes 10336 cm3 to do.
That's the equivalent of a 1m x 1m x 1.03cm block
Using Lead (which traditional ballast is made out of, which is why I chose lead), that 1m x 1m block would have to be 1.76cm thick, to make up the 17621cm3.
Put in another way, you need 170%, or 70% more lead by volume to make up the same mass.
So, to make sense of what I just said: F1 teams like tungsten because it is dense, and they don't have to pack as much of it into a chassis to reach the required weight. but is not expensive like Osmium, Iridium, Platinum, and Rhenium. But some teams don't care about expenses.
Ballast must be fixed, and by FIA rules can't be movable in any time of the race.
