Question

Why do we prefer spanner of longer arm compared to spanner of shorter arm

Answer 1

A longer arm will allow the same torque on the Bolt / Nut with less force applied at the end. Spanners work by transferring a moment ( force x distance ) from your hand into a moment onto the nut ( small distance x very much larger force ).

Answer 2

we prefer a spannel with long arm as it is further away from the pivot thus giving us more moment and it shows better results