Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: In a wheel and axle, force may be applied either to the wheel or to the axle. This force is called the input force. A wheel and axle does not change the direction of the input force. However, the force put out by the machine, called the output force, is either greater than the input force or else applied over a greater distance. Answer: input force
Output:
What is the term for the force applied to a wheel and axle?