Inclined Planes
On a slope, weight splits into components along and perpendicular to the surface.
About this topic
On a slope of angle θ, weight mg splits into a component parallel to the slope, mg sin θ, which drives the object downhill, and a component perpendicular to it, mg cos θ, balanced by the normal force. Without friction, a = g sin θ.
With friction, the net force is mg sin θ - μmg cos θ. An object starts to slide when tan θ exceeds the coefficient of static friction, so the angle at which it begins to slip lets you measure μ. A ramp reduces the force needed to lift a load, but the force acts over a longer distance.
Example: a 5 kg crate on a frictionless 30 degree ramp accelerates at 9.8 x 0.5 = 4.9 m/s² down the slope. The normal force is 5 x 9.8 x cos 30, about 42 N. Wheelchair ramps, loading ramps, ski slopes and mountain roads with switchbacks use these ideas.
Tips: tilt your axes so that one runs along the slope. A frequent mistake is to use cos where sin belongs. Check by thinking about limits: on a flat surface (0 degrees) the parallel component should be zero, which matches sin 0 = 0.
Key ideas
- Along slope: mg sin θ
- Perpendicular: mg cos θ
- Steeper slopes mean bigger acceleration
Quick check
Use cases: where Inclined Planes helps
- Homework: review the key idea behind Inclined Planes before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Inclined Planes without notes.
- Visual learning: play with the interactive lab to see how Inclined Planes changes when you adjust its inputs.
- Teaching a friend: explain Inclined Planes in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Inclined Planes?
On a slope, weight splits into components along and perpendicular to the surface.
What will I learn in Inclined Planes?
Along slope: mg sin θ. Perpendicular: mg cos θ. Steeper slopes mean bigger acceleration.
Is Inclined Planes part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Inclined Planes lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Inclined Planes?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.