Investigating Friction with an Inclined Plane

Friction is one of the most familiar yet misunderstood forces in physics. Using an inclined plane, students can measure and understand how friction opposes motion, how it depends on surface type, and how it relates to the angle of the slope.

---

The Experiment

A small wooden or metal ramp is set up so that its angle can be adjusted gradually. A block or PASCO dynamics cart is placed on the surface.

Students:

1. Increase the angle slowly until the block just begins to slide — this angle is used to calculate the coefficient of static friction. My inclined plane has a measurement scale on it, but it is not very accurate, so we use a mobile phone with an inclinometer app on it

2. Use a force sensor to measure the force needed to keep the block moving at constant speed, showing the kinetic friction.

3. Compare how different surfaces — wood, plastic, felt, sandpaper — affect results.

---

The Science

The key relationship for the coefficient of static friction is:

$$\mu_s = \tan(\theta)$$

where $\theta$ is the angle at which the object begins to slide.

The higher the angle, the greater the coefficient of friction. Students can compare static friction (force needed to start motion) with kinetic friction (force needed to maintain motion).

This experiment links to Newton’s laws and the balance of forces acting parallel and perpendicular to the surface.

---

Skills Highlight

• Measuring forces using sensors and interpreting vector components

• Calculating coefficients of friction from experimental data

• Understanding the difference between static and kinetic friction

• Relating experimental results to everyday examples — tyres, shoes, and machinery

---

Why It Works in Teaching

The inclined plane turns an abstract force diagram into something real and measurable. Students can see the transition from rest to motion, test different materials, and understand why friction is sometimes helpful and sometimes a hindrance.