A bell bollard is a style of bollard designed to deflect vehicle tires. The wheel mounts the lower part of the bollard and is deflected by its increasing slope. Such bollards are effective against heavy goods vehicles that may damage or destroy conventional bollards or other types of street furniture. A variant on the bell bollard is the Martello bollard, its sloped shape inspired by the profile of historic Martello towers. Removable bollards Bollards may be hinged at ground level, allowing them to be folded flat to permit vehicles to drive over them.
In stoichiometry calculations, we assume that reactions run to completion. However, when a chemical reaction is carried out in a closed vessel, the system achieves equilibrium. Equilibrium occurs when there is a constant ratio between the concentration of the reactants and the products. Different reactions have different equilibria. Some may appear to be completely products, however, all reactions have some reactants present.
Reactions occur all the time. However, certain prequisites must be fulfiled before a reaction can occur. You cannot say, expect a reaction to occur between one substance and another if you keep both of them separated. Therefore, one theory that discusses how reactions occur is The collision theory. In the collision theory, for the reaction to occur reactants involved together must: Collide with the right orientation. Collide with sufficient energy.