Laws of Motion Cheatsheet

Cheat Codes & Shortcuts

• First Law (Inertia): An object remains at rest or in uniform motion unless acted upon by an external force.
• Second Law: \( F = ma \), where \( F \) is the net force, \( m \) is mass, and \( a \) is acceleration.
• Third Law: For every action, there is an equal and opposite reaction.
• Net Force: Sum of all forces acting on an object: \( \vec{F}_{\text{net}} = \sum \vec{F}_i \).
• Weight: \( W = mg \), where \( g \) is gravitational acceleration (\( 9.8 \, \text{m/s}^2 \)).
• Friction: \( f = \mu N \), where \( \mu \) is the coefficient of friction and \( N \) is the normal force.
• Momentum: \( \vec{p} = m \vec{v} \), where \( \vec{v} \) is velocity.
• Impulse: \( \vec{J} = \Delta \vec{p} = \int \vec{F} \, dt \).
• Equilibrium: If \( \vec{F}_{\text{net}} = 0 \), the object is in equilibrium (no acceleration).
• Free-Body Diagram: Diagram showing all forces acting on an object.

Quick Reference Table

Type	Concept	Formula/Application
First Law	Object at rest or constant velocity	\( \vec{F}_{\text{net}} = 0 \)
Second Law	Force causes acceleration	\( \vec{F} = m \vec{a} \)
Third Law	Action-reaction pairs	\( \vec{F}_{A \text{ on } B} = -\vec{F}_{B \text{ on } A} \)
Friction	Opposes motion	\( f = \mu N \)
Momentum	Mass in motion	\( \vec{p} = m \vec{v} \)
Impulse	Change in momentum	\( \vec{J} = \Delta \vec{p} \)

Advice

Laws of Motion Quick Tips

• First Law: Objects resist changes in motion—think inertia!
• Second Law: Use \( F = ma \) to find acceleration or force.
• Third Law: Action-reaction forces act on different objects, not the same one.
• Friction: Calculate normal force first, then use \( f = \mu N \).
• Momentum: For collisions, use conservation of momentum: \( \vec{p}_{\text{initial}} = \vec{p}_{\text{final}} \).

Laws of Motion Speed Quiz

Test your speed with 5 Laws of Motion questions! You have 30 seconds per question.