A machine of velocity ratio 6 requires an effort of 400 N to raise a load of 800 N through I m. Find the efficiency of the machine

Analyze the question

We are given a machine with velocity ratio (VR) = 6, effort = 400 N, and load = 800 N. We need the efficiency.

Concept

• Mechanical advantage (MA) = Load / Effort
• Efficiency = (MA / VR) × 100%

(The "1 m" is the distance the load moves. It isn't needed here because VR is already given.)

Solution

1. MA = 800 / 400 = 2
2. Efficiency = (MA / VR) × 100 = (2 / 6) × 100
3. Efficiency = 0.3333 × 100 = 33.3%

Answer: C (33.3%)

Tip: Efficiency = MA/VR × 100%. It is also work output / work input. As a check, the effort moves 6 m, so the input work is 400 × 6 = 2400 J. The output work is 800 × 1 = 800 J. 800/2400 = 33.3%. Both methods give the same result, so use whichever is quicker. Efficiency can never exceed 100%, which helps you rule out impossible options.