Physics of the kick
Of all the different kicks in a TaeKwon Do arsenal, the front kick would have to be the most basic. So I will concentrate on explaining this one. To properly perform this technique,
one must first chamber the leg and then
accelerate it toward your target, striking it with
the ball of the foot with the toes bent upward. Chambering occurs when you bring your leg to a fixed, bent position (90 degrees), about waist high, before executing the kick. Chambers are used in all aspects of TaeKwon Do; kicks, punches, blocks, and pomsae (forms).
A rear round kick is the most commonly used kicks in TaeKwon Do. It also can be one of the most powerful.
 

Also, since TaeKwon Do is primarily a kicking art, the majority of movements are kicks. All kicking techniques should be performed with maximum power toward your target, unless of course you are sparring. When kicking, your legs should not exceed shoulder width. This makes the kicks faster and harder to detect when fighting.  Kicks are your number one offensive weapon in
TaeKwon Do and should be dealt with tremendous force and precision. To create a great amount of momentum in your kicks, a high velocity is the best way to go. Also, a high velocity will greatly enhance the energy in your techniques.