Physics/Mechanics/Principles and Exploration
Inclined plane and friction — principles and investigation
Why doesn't an object slide right away even if the slope is slightly tilted? This is an experiment that compares the component of gravity that pulls downward and the static friction force that supports it. Examine the difference between static friction and kinetic friction, distinguishing between the boundary starting to move and the acceleration after it moves.
How does it work?
The critical angle at rest is independent of mass. When the boundary is crossed, the acceleration is calculated from the coefficient of kinetic friction.
tanθc = μs · a = g(sinθ − μk cosθ)
Try this investigation
- Change the inclination angle and observe the blocks and force arrows. I leave it at a standstill every time.
- Fix the friction coefficient at μs = 0.40, μk = 0.25. Record the states and acceleration of 15°, 22°, and 30°.
- At 30°, change the mass to 1 kg and 5 kg and record it. Compare acceleration and friction together.
Interpreting your results
What are the boundary conditions before a stationary object slips?
Since mg sinθ = μs mg cosθ, tanθ = μs. If you cross the border, you'll slip.
Assumptions and limitations
The moment at exactly tanθ = μs is left at limit rest. If you go a little beyond this, it will slip. Ignore air resistance, rotation, and surface changes. Observe in the downward direction for up to 4 m or 3 s, and observe at rest for 2 s.