Final answer:
The statement that efficient machines increase effort force (input) is NOT true. Efficient machines are intended to reduce the input force, often by increasing the distance over which that force is applied or changing the direction of the force, while maintaining the same output work.
Step-by-step explanation:
Which of the following is NOT true of efficient machines? The correct option that is NOT true of efficient machines is that they increase effort force (input). This is because efficient machines are designed to reduce the input force needed to perform a job while still being able to do the same amount of work. Simple machines achieve this by changing the distance over which the force must be applied or changing the direction of the applied force. Mechanical advantage is the ratio of output force to input force in a machine, and the goal of a simple machine is to increase this mechanical advantage, thereby reducing the input force required. Efficient machines indeed can change the direction of an applied force, increase the distance over which a force is applied, and increase resistance force (output), but they do not increase the input force since that would make the machine less efficient.