Newton’s laws: forces and free-body diagrams

What you’ll work on

Build confidence with Newton’s 1st, 2nd, and 3rd laws by turning words and pictures into correct free-body diagrams (FBDs) and net-force statements. You’ll practice identifying all forces, choosing sign conventions, and connecting ΣF to acceleration.

Each question is multiple-choice with 4 options and no timer, so you can reason carefully instead of rushing. Before you start, choose how many questions you want and select a difficulty level; “Mixed” blends easier recognition tasks with multi-step setups.

Common pitfalls to avoid

Many mistakes come from missing forces (like friction or tension), mixing up action–reaction pairs, or drawing forces that belong on the other object. Another frequent slip is using the wrong component of weight on an incline or choosing axes that make the algebra harder than it needs to be.

• Separate forces acting on the object from forces the object exerts on others
• Include normal force correctly (not always equal to weight)
• Resolve weight into components on ramps and angled motion
• Treat friction direction based on relative motion/impending motion
• Use ΣF = ma per axis with consistent signs and units

How the difficulty stays balanced

Difficulty is balanced by mixing quick concept checks (identify forces, match laws) with calculation-based items (net force, acceleration, tension, friction). Mixed mode ensures you get variety without long streaks of only easy or only heavy-math questions.

Use shorter question counts for focused drills (like FBD accuracy) and longer runs for exam-style endurance. If you’re stuck, slow down and redraw the diagram—most problems become straightforward once the FBD is correct.