See the alternating Red and White stripes behind the Red Bull Car? You can kind of assume that to be the Apex. To be precise, the Apex is the exact center of the highest point on the Red-White Striped area.
Another, more simpler way to describe the Apex would be to call it the geometric Center of a Turn. Have a look at the following Picture
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Notice the three differently colored lines. One of the most important requirements for a good racing driver is to be able to identify the most ideal racing line to follow around a track.
The first thing that you will notice is that all three lines pass through a single point. This point is termed the ‘Apex’. You might wonder why all the three racing lines pass through the Apex. Why not just stay on the center of the track? The reason is quite simple. The tyres on a Formula One car are reasonably grippy, and the steering is pretty sharp. But the fact remains that If a driver attempted to do a complete 90 degree turn, it would put a lot of stress on the tyres, brakes and the general setup of the car. The driver has to first brake and slow the car down as much as possible, steer the car by about 90 degrees and then set off again. Moreover, this would lead to a significant loss in Lap times.
By making use of the Apex, The Driver can approach the corner at a higher speed and brake later. This also helps in exiting the corner quickly. Entry, Apex and Exit comprises how a turn is completed in Minimum time taken. Cornering is an art that a Driver has to master because he has to able to judge the perfect point when to brake. Moreover, on exiting the Apex he has to be quick on stepping on the throtle and getting the car back upto speed.
The Green Line is the Ideal Racing Line for any car under normal Circumstances. On a normal sunny day when all you want to do is set as many Quick Laps as possible, this should be your preferred racing line. The Blue Racing Line Generally comes into the Picture when your car setup is such that you can afford to brake as late as possible. This Line is also most commonly used during Overtaking Maneuvers.
The Apex thus plays a very important role in improving the efficiency and reliability of an F1 car. Moreover, the various racing lines available to the drivers has made for some spectacular battles and overtakings over the years.
Formula One Simplified 