How is efficiency determined if the AMA is 4?

Efficiency in a machine is calculated by comparing the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). The formula for efficiency is given by:

Efficiency (%) = (AMA / IMA) × 100

In this scenario, it is provided that the AMA is 4. To determine the efficiency, one needs the IMA value. The IMA is defined by the design of the machine and represents the theoretical maximum advantage of the machine without accounting for losses due to friction or other factors.

If we assume a scenario where the IMA is considered to be 5 for this example, the efficiency calculation would be as follows:

Efficiency = (4 / 5) × 100

Efficiency = 0.8 × 100 = 80%

This confirms that the efficiency is 80%, making the answer correct. This percentage reflects how effectively the machine converts input work into output work, indicating that while the machine does provide a benefit, there is still a loss present, likely due to friction or other inefficiencies in the system.

Understanding this relationship helps clarify why the efficiency can typically reach up to 100% only in an ideal scenario, while real machines, with actual mechanical advantages, often reflect lower efficiency values.