Which statement best defines a simple machine?

• A. Changes the magnitude or direction of a force with less effort
• B. Converts energy from one form to another with no loss
• C. Requires electricity to operate
• D. Increases the friction in a system

Answer: (A)

A simple machine is a device that changes the size or direction of a force so you can do the same work with less effort. This captures the idea of mechanical advantage: you apply a smaller force (or push in a different direction) and still move the load because work input and output are balanced (ignoring friction).

Think of a lever or an inclined plane. A lever lets you lift a load with less force by increasing the distance over which you apply it. An inclined plane lets you push or pull over a longer distance with a smaller force. These examples show how the machine makes work easier by altering the force or its direction.

The other statements aren’t defining features of simple machines: energy can be transformed between forms, but that doesn’t define a simple machine and real systems involve some losses. Requiring electricity is not necessary, since many simple machines operate without power. Increasing friction is the opposite of what a simple machine aims to do, which is to reduce the effort needed.