fill in the blanks

Question

An efficient simple machine is one that converts BLANK into a useful form of BLANK. For example, a pulley converts almost BLANK of the energy used pulling on the rope into lifting an object.
Output energy.
Input energy.
None.
All.

Answer 1

An efficient simple machine is one that converts input energy into a useful form of output energy. For example, a pulley converts almost all of the energy used pulling on the rope into lifting an object.