A resistance arm is the part of a lever that moves against weight or resistance. It works in conjunction with the force arm to move an object. Ideally, it is the distance between the axis and the point of weight or resistance.
The length of a resistance arm is similar to the distance between the load and the fulcrum. A lever can either have a long resistance arm or a short resistance arm. A long resistance arm implies speed and range of movement, while a short resistance arm implies greater force. The formula of calculating the resistance arm is F*FA =R*RA.