The rate of effusion states that the rate of a gas is inversely proportional to the square of their mass. So that means rate of gas equals 1m of molar mass.
But what exactly does that mean? Well in simple terms it means increasing the molar mass of a gas means that we are going to lower its speed and the lower its rate.
So basically the more a gas particle or molecule weighs, then the slower it's going to move. So that's basically the idea behind the rate of a fusion.