The rate at which the chemical reaction occurs is controlled by a number of factors and catalyst is the most suitable answer because irrespective of the type of reactants involved and the type of reaction, a catalyst always increases the speed of the reaction no mater what as it is independent. Other factors which influences the reaction rate are temperature, increasing the concentration of the reactants, e.t,c.
Answer: The greatest force of gravity on the ball will occur at the point when the ball is near to hit the ground ... hope this helps have a good day :P
