Name two simple machines and describe how they reduce effort.

• A. Lever and pulley; they increase speed.
• B. Wedge and screw; they change the direction of force.
• C. Pulley and inclined plane; they reduce friction.
• D. Lever and inclined plane; they increase distance or change the direction of force to reduce effort.

Answer: (D)

Two simple machines reduce the effort needed to do work by changing either the direction of the applied force or the distance over which you apply it. A lever uses a fulcrum to create mechanical advantage: when you place the effort farther from the fulcrum, you can lift a heavier load with less force because the load moves a shorter distance relative to your hand’s movement. An inclined plane lets you push a load up a ramp, spreading the work over a longer distance and along the slope, so the force you must apply at any moment is smaller even though you move the load farther. This combination shows how changing direction and increasing distance in these machines lowers the effort required.