Physics is mostly free-body diagrams (and how to draw them)

Ask a strong physics student how they start a forces problem and they all say the same thing. Draw the free-body diagram first. The students who struggle usually skip it and jump straight to equations, and then they wonder why the signs never work out.

The routine

1. Draw the object as a dot. Forget the ramp and the rope for a second. Just the object.
2. Add every force as an arrow from that dot. Gravity straight down, the normal force perpendicular to the surface, tension along the rope, friction opposing motion. One arrow per force, no more.
3. Pick axes that make life easy. On a ramp, tilt your axes so one runs along the slope. That turns one ugly problem into two clean ones.
4. Write the sum of forces equals ma for each axis. Now the equations come straight off your arrows, and the signs match.

The two mistakes I see most

First, inventing forces that aren't there. There's no separate "force of motion" pushing a sliding box. Second, forgetting to break gravity into components on a ramp. Both disappear the moment the diagram is honest.

The diagram is the physics. Once the arrows are right, the algebra is just bookkeeping.

Next time you're stuck on a forces question, don't reread the chapter. Redraw the diagram, slowly. Nine times out of ten the mistake is sitting right there in a missing or an extra arrow.