This simulator hoists a hanging load with a block and tackle and lets you choose how many rope parts support the moving block. It shows the trade-off at the heart of every simple machine: a smaller pull on the rope is paid for with a longer length of rope pulled.
• A 3D fixed pulley block, traveling block, continuous reeved rope, suspended load and free-end pull that you can orbit and inspect. • Controls for supporting rope parts (two or four), lifted mass (10-100 kg), hoist efficiency (0.6-1) and pulling speed (0.1-0.8 m/s). • Six live readouts: required hand force, load weight, load travel, hand travel, input work and potential energy gained. • Two presets: Four supporting parts (effort is a quarter of the load weight, hand distance four times the load distance) and Friction costs work (input work exceeds potential-energy gain).
The ideal mechanical advantage equals the number of supporting rope parts, n. The required effort is F = m g / (n eta), where eta is the hoist efficiency. Because the rope parts share the lift, load travel is y = s_hand / n. Input work is F times hand travel, useful work is m g y, and the difference is the lost work. With n = 4 and eta = 1 the hand force is a quarter of the weight but the hand moves four times as far, so the work is unchanged.
The lift is quasistatic with a massless rope and pulleys, no slip and no rope stretch, and it stops at 1.5 m of load travel. Efficiency is an aggregate loss factor, not a solution for local rope tension at each sheave. Ropes and sheaves are enlarged and representative. Lower the efficiency and watch the extra input work appear as loss rather than as extra load energy.
No. In the ideal case the work is the same; you exchange force for distance. With real friction the input work is actually larger than the potential energy gained.
The number of rope parts supporting the moving block. Two parts halve the required force and four parts quarter it, in the ideal lossless case.
Required effort is divided by efficiency, F = m g / (n eta), so a less efficient hoist needs a larger pull for the same load and the extra work appears as loss.
It is a quasistatic model with a massless, non-stretching rope and pulleys, an aggregate efficiency factor rather than a per-sheave friction solution, and a 1.5 m lift limit.