We know gravity is equal everywhere that is 9.8 then why some material float on water and some sink in water? and also tell me everywhere buoyant force in water is equal?if yes than every substance would float on water and if no then why? Experts please answer it . urgent

Dear student, Gravity is same means every object exert force equal to it's weight on water downward. But buyouant force depends upon the volume of water that the object replaces. If weight of that replaced water is greater than weight of the body then body will float. Otherwise body will sink if its weight is greater than the weight of water replaced by its volume. So this is the basic reason why body float or sink in water. It's not about their weight only it's about what volume of water they are replacing. Regards