5.1. Mechanical efficiency

Try these first

1. 1.

   What is the formula for mechanical efficiency?

   Hint

   Think about what you need to calculate both work output and energy input.

2. 2.

   If a machine has a useful output of 20 J and input energy of 25 J, what is the mechanical efficiency?

   Hint

   Use the formula provided to find your answer.

3. 3.

   What is mechanical efficiency?

   • The ability to do work
   • The ratio of useful work output to energy input
   • The total energy input to a machine

   Hint

   Focus on what is measured against what is used.

4. 4.

   True or False: A higher mechanical efficiency indicates more waste in energy.

   • True
   • False

   Hint

   Think about the goal of efficiency.

5. 5.

   A machine operates with an input energy of 600 J and produces a useful output of 420 J. If improvements are made that boost the input energy to 800 J without changing the output, what will be the new efficiency?

   Hint

   Remember to use the efficiency formula for the new values.

6. 6.

   If two engines have mechanical efficiencies of 95% and 80%, respectively, and they both input 1000 J, how much useful work do they produce?

   Hint

   Calculate each one using their respective efficiencies.