Differential pulley load, and an endless rope looped around the pulleys. To avoid slippage, the rope is usually replaced by a chain, and the connected pulleys by sprockets. The two sections of chain carrying the single pulley exert opposing and unequal torques on the connected pulleys, such that only the "difference" of these torques has to be compensated manually by pulling the loose part of the chain. This leads to a mechanical advantage: the force needed to lift a load is only a fraction of the load's weight. At the same time, the distance the load is lifted is smaller than the
Tackle (gridiron football position) Tackle (gridiron football position) Tackle is a playing position in American and Canadian football. Historically, in the one-platoon system prevalent in the late nineteenth and early twentieth centuries, a tackle played on both offense and defense. In the modern system of specialized units, offensive tackle and defensive tackle are separate positions, and the stand-alone term "tackle" refers to the offensive tackle position only. The offensive tackle (OT, T) is a position on the offensive line, left and right. Like other offensive linemen, their job is to block: to physically keep defenders away from the offensive player who has the football