[06.25.2025] Updated content, AnKing-MCAT/AnKingMed, ID 3505220

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Hi! Thanks for the suggestion. Please correct me if I am wrong but the force of friction on an inclined plane is = umgcos(theta)

I think I see where the confusion might be coming from. On a lot of MCAT practice questions, we see:

Friction = mgsin(theta)

But that’s true only when the object is sliding at constant velocity, meaning the friction force is exactly balancing the component of gravity pulling it down the incline. That’s a special case where the net force = 0.

More generally, though, the force of friction is defined as:

umgcos(theta)

Because friction depends on the normal force, which is perpendicular to the inclined surface, not the downslope gravitational force.