Question

The output energy of a real-life machine is less than input energy because of :

• A. moving parts of machine
• B. friction at the moving parts
• C. both (A) and (B)
• D. none of these

Answer 1

The correct option is B

friction at the moving parts

1. The output work is always less than the input work because some input work is used to overcome friction.
2. Therefore, efficiency is always less than 100%.
3. All machines make work easier, but they don’t increase the amount of work that is done.
4. Efficiency is the percent of work put into a machine by the user (input work) that becomes work done by the machine (output work).
5. The output work is always less than the input work because some input work is used to overcome friction.

Hence, option B is correct.