$W_in = 50\text N \times 0.5\text m = 25\text J$
Because some of the input work is always converted into thermal energy (heat) due to friction, and is also lost as sound and vibration, rather than being used to perform useful work. In an ideal (frictionless) machine, efficiency would be 100%, but such conditions do not exist in the real world. $W_in = 50\text N \times 0
The mechanical advantage that a machine provides in real-world conditions. It takes into account the energy lost due to friction. 2. Efficiency efficiency would be 100%