Mechanical Advantage and Chemical Properties

Posted on May 22, 2026 in Chemistry

Understanding the Three Classes of Levers

Levers are simple machines used to gain mechanical advantage.

First-Class Levers

First-class levers change the direction of force. Changes direction of force. Changes direction of force.

• Case 1: D_IN = D_OUT, F_IN = F_OUT, MA = 1. Benefit: Changes direction of force. Drawback: No force or distance benefits. Example: See-saw, Scissors.
• Case 2: D_IN < D_OUT, F_IN > F_OUT, MA < 1. Benefit: D_IN < D_OUT. Drawback: F_IN > F_OUT. Example: Catapult.
• Case 3: D_IN > D_OUT, F_IN < F_OUT, MA > 1. Benefit: F_IN < F_OUT. Drawback: D_IN > D_OUT. Example: Crowbar.

Second-Class and Third-Class Levers

Second-Class Levers

• Properties: D_IN > D_OUT, F_IN < F_OUT, MA > 1.
• Pros/Cons: + F_IN < F_OUT; – D_IN > D_OUT.
• Examples: Paper cutter, nutcracker, wheelbarrow.

Third-Class Levers

• Properties: D_IN < D_OUT, F_IN > F_OUT, MA < 1.
• Pros/Cons: + D_IN < D_OUT; – F_IN > F_OUT.
• Examples: Arm, baseball bat, croquet mallet, paintbrush.

Principles of Motion and Force

• Speed: Distance / Time (m/s).
• Velocity: Distance / Time in a specific direction (m/s→).
• Acceleration: (Final Velocity – Initial Velocity) / Time (m/s²→). An object can accelerate, decelerate, or change direction.
• Force: A push or a pull.

Work, Power, and Efficiency Formulas

• Mechanical Advantage (MA): F_OUT / F_IN (no label).
• Work In: F_IN x D_IN (N·m or Joules).
• Work Out: F_OUT x D_OUT (N·m or Joules).
• Efficiency: (Work Out / Work In) x 100%.
• Ideal Conditions: Efficiency = 100%, Work Out = Work In.
• Pulleys: MA = number of supporting strings. Final strings pulling up count; final strings pulling down do not. MA = D_IN / D_OUT.
• Ramps: MA > 1; + F_IN < F_OUT; D_IN > D_OUT.
• Work: Force x Distance (Joules or Newton-Meters).
• Power: Work / Time or (Force x Distance) / Time (Watts, Joules/second, or Newton-Meters/second).

Interpreting Motion Graphs

• Position/Time Graphs: Measure distance from a specific point; direction is important. It is possible for a position/time graph to go down.
• Distance/Time Graphs: Measure meters moved without paying attention to direction.

Classification of Matter and Mixtures

• Matter: Anything that has mass and takes up space.
• Mixture: Two or more substances mixed together but not chemically combined; they do not act like a new substance when mixed together.
• Heterogeneous Mixture: Two or more substances mixed but not chemically combined; you can see different parts of the mixture. Example: Suspension (mixture with large particles suspended in each other).
• Homogeneous Mixture: Cannot see individual particles.
• Solution: Solute dissolved in a solvent.
• Alloy: A solution of metals.
• Colloid: One substance suspended but not dissolved.

Elements, Atoms, and Chemical Compounds

• Pure Substance: Contains only one type of particle.
• Element: Contains only one type of atom (118 known elements).
• Atom: The smallest whole piece of an element that acts like that element.
• Diatomic Element: Elements that naturally occur with two atoms bonded together (e.g., O₂).
• Chemical Symbol: One capital letter, sometimes followed by a lowercase letter.
• Compound: Two or more elements mixed together and chemically combined.
• Molecule: The smallest piece of a compound.
• Chemical Formula: Tells you the types of elements and the number of atoms.
• Subscript: A number that affects the element immediately preceding it.
• Coefficient: A number that comes before the chemical formula to tell you how many “packages” or molecules there are.