Friction

Friction

Friction is a force that resists motion between two surfaces in contact. It plays a crucial role in natural and engineered systems, helping objects start, stop, or slow down. Friction can be useful, such as providing traction for walking, or undesirable, such as causing wear in machines. Its strength depends on the surfaces involved and the force pressing them together. By studying friction, scientists and engineers design better products, improve efficiency, and solve problems caused by resistance between surfaces.

Science and Engineering Practices (SEP): Planning and Carrying Out Investigations

Friction can be explored by testing how different surfaces or materials affect how objects move. By changing one thing at a time—like the surface or adding something slippery—you can see how friction increases or decreases.

Activity Ideas:

• Surface Test – Pull an object, like a toy car, across different surfaces such as wood, carpet, tile, or sandpaper. Measure how hard it is to move the toy car on each surface and compare how surface texture affects friction.
• Friction and Slippery Surfaces – Repeat the test using soap, oil, or water on a wooden surface. Observe how these slippery materials reduce friction and make it easier to slide the toy car.
• Shoe Sole Investigation – Examine the bottoms of different shoes to see which ones grip the ground best. Test how easily each shoe slides on the floor and explore why some soles create more friction than others.

These activities demonstrate friction’s effects in daily life and show how materials and surfaces impact motion.

Crosscutting Concept (CCC): Stability and Change

Friction affects how things stay stable or change over time:

• Stability – High-friction soles improve grip, prevent slipping, and provide balance, especially on smooth or wet surfaces.
• Change – Friction wears down tires, brakes, and other parts, reducing performance and requiring maintenance or replacement.
• Scale – Even smooth-looking surfaces have microscopic bumps and ridges. Friction occurs when these irregularities interact, producing effects observable in larger systems.