Laws of Motion and Friction: One-Page Formula Sheet

Laws of Motion and Friction — formula sheet

Formulas

• F_net = ma = dp/dt
• f_s ≤ μₛN, f_k = μₖN
• Banked road (no friction): tanθ = v² / rg
• Impulse J = FΔt = Δp

Key ideas

• Draw a free-body diagram for each body before writing equations
• Static friction adjusts up to μₛN; kinetic friction is μₖN
• Pseudo force −ma acts in a non-inertial frame
• In circular motion the net force towards the centre is mv²/r

Traps to avoid

• Assuming friction always equals μN
• Forgetting the normal force changes on an incline or with an applied angled force
• Treating centripetal force as an extra force on the FBD

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