<P> Each athlete has a set amount of time in which to make an attempt . The amount of time varies by level of competition and the number of vaulters remaining . If the vaulter fails to begin an attempt within this time, the vaulter is charged with a time foul and the attempt is a miss . </P> <P> Poles are manufactured with ratings corresponding to the vaulter's maximum weight . Some organizations forbid vaulters to use poles rated below their weight as a safety precaution . The recommended weight corresponds to a flex rating that is determined by the manufacturer by placing a standardized amount of stress (most commonly a 50 lb (23 kg) weight) on the pole and measuring how much the center of the pole is displaced . Therefore, two poles rated at the same weight are not necessarily the same stiffness . </P> <P> Because pole stiffness and length are important factors to a vaulter's performance, it is not uncommon for an elite vaulter to carry as many as ten poles to a competition . The effective properties of a pole can be changed by gripping the pole higher or lower in relation to the top of the pole . The left and right handgrips are typically a bit more than shoulder width apart . Poles are manufactured for people of all skill levels and body sizes, with sizes as short as 3.05 m (10 ft 0 in) to as long as 5.30 m (17 ft 5 in), with a wide range of weight ratings . Each manufacturer determines the weight rating for the pole and the location of the maximum handhold band . </P> <P> However speed is the most essential element to higher jumps, because the energy produced by the run (1 2 m v 2 (\ displaystyle (\ frac (1) (2)) mv ^ (2)), m (\ displaystyle m) = mass of the athlete; v (\ displaystyle v) = speed) is converted to vertical propulsion (gravitational potential energy) (mass x height x acceleration due to gravity (9.81 m s − 2 (\ displaystyle 9.81 ms ^ (- 2)))). </P>

What is the length of a pole vault