Friction of a Block on an Inclined Plane

A block is placed on a flat board that can be tilted to form an inclined plane. As the incline is raised, the block remains at rest until the downhill pull of gravity overcomes static friction, at which point it begins to slide. The angle at which sliding begins can be used to measure the coefficient of static friction, while constant-speed sliding demonstrates kinetic friction.

1. Place one of the blocks on the flat incline.
2. Slowly raise the incline until the block just begins to slide.
3. Record the angle at which sliding starts; this corresponds to the coefficient of static friction.
4. To measure kinetic friction, set the incline at a slightly greater angle and gently start the block sliding.
5. Adjust the incline until the block moves at constant speed; record this angle to determine the coefficient of kinetic friction.
6. Repeat the demonstration with different blocks and surfaces to compare results.

Slide blocks down incline - UCSB Physics Lecture Demonstrations:

Dynamics Demo: Inclined Plane - Physics Demos:

📄 Slide blocks down incline - UCSB Physics Lecture Demonstrations: https://web.physics.ucsb.edu/~lecturedemonstrations/Composer/Pages/12.69.html

• Use different block surfaces (wood, sandpaper, mylar, rubber, aluminum, polyethylene) to compare friction.
• Place a brass-clad plate on the incline to change the sliding surface.
• Try the smaller classroom version with an angle scale for easier measurement.

• Ensure the incline is stable before releasing the block.
• Keep hands and fingers clear of the sliding block.
• Do not use very heavy blocks that could cause injury if they fall.

• Why does the block remain at rest at small angles? (Because static friction balances the downhill pull of gravity until it reaches its maximum value.)
• Why is the angle for constant sliding different from the angle at which sliding starts? (Kinetic friction is slightly less than static friction.)
• How does changing the surface material affect the angle at which sliding begins? (Different materials have different coefficients of friction.)