Study guide
10.2 Core Concepts: Forces, Energy, and Simple Machines
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1 Chapter 1: AFOQT Orientation and Exam Strategy
1.1 Current AFOQT Exam Facts 1.2 Eligibility, Application, and Scheduling 1.3 Blueprint Domains and Weighting 1.4 Question Style and Score Report Thinking 1.5 Study Calendar and Practice Plan
2 Chapter 2: Verbal Analogies
2.1 Verbal Analogies Overview 2.2 Core Workflows and Decision Points 2.3 Scenario Practice for Verbal Analogies 2.4 Common Traps in Verbal Analogies 2.5 Practice Drills and Readiness Markers
3 Chapter 3: Arithmetic Reasoning
3.1 Arithmetic Reasoning Overview 3.2 Core Problem Types and Solution Workflows 3.3 Scenario Practice and Translation Method 3.4 Common Traps in Arithmetic Reasoning 3.5 Practice Drills and Readiness Markers
4 Chapter 4: Word Knowledge
4.1 Word Knowledge Overview 4.2 Decoding Words: Roots, Prefixes, and Suffixes 4.3 Working a Synonym Question Step by Step 4.4 Common Traps in Word Knowledge 4.5 Practice Drills and Readiness Markers
5 Chapter 5: Math Knowledge
5.1 Math Knowledge Overview 5.2 Core Algebra and Geometry Workflows 5.3 Worked Problem Walkthroughs 5.4 Common Traps in Math Knowledge 5.5 Practice Drills and Readiness Markers
6 Chapter 6: Instrument Comprehension
6.1 Instrument Comprehension Overview 6.2 Reading the Attitude Indicator and Compass 6.3 Matching the Dials to the Silhouette Airplanes 6.4 Common Traps in Instrument Comprehension 6.5 Practice Drills and Readiness Markers
7 Chapter 7: Block Counting
7.1 Block Counting Overview 7.2 Core Workflows and Decision Points 7.3 Scenario Practice for Block Counting 7.4 Common Traps in Block Counting 7.5 Practice Drills and Readiness Markers
8 Chapter 8: Table Reading
8.1 Table Reading Overview 8.2 Core Lookup Workflow and Speed Technique 8.3 Reading the Grid: Worked Lookups 8.4 Common Traps in Table Reading 8.5 Practice Drills and Readiness Markers
9 Chapter 9: Aviation Information
9.1 Aviation Information Overview 9.2 Aerodynamics and Flight Controls 9.3 Aircraft Structure, Engines, and Instruments 9.4 Airport Operations, Markings, and Common Traps 9.5 Practice Drills and Readiness Markers
10 Chapter 10: General Science
10.1 Physical Science Overview 10.2 Core Concepts: Forces, Energy, and Simple Machines 10.3 Waves, Heat, and the Electromagnetic Spectrum 10.4 Chemistry and Electricity Essentials 10.5 Earth/Space Science and Practice Drills
11 Chapter 11: Situational Judgment
11.1 Situational Judgment Overview 11.2 Core Workflows and Decision Points 11.3 Scenario Practice for Situational Judgment 11.4 Common Traps in Situational Judgment 11.5 Practice Drills and Readiness Markers
12 Chapter 12: Reading Comprehension
12.1 Reading Comprehension Overview 12.2 Core Reading Methods and Question Types 12.3 Scenario Practice for Reading Comprehension 12.4 Common Traps in Reading Comprehension 12.5 Practice Drills and Readiness Markers
13 Chapter 13: Self-Description Inventory
13.1 Self-Description Inventory Overview 13.2 The Big Five and Response Strategy 13.3 Scenario Practice: Reading SDI Statements 13.4 Common Traps in the Self-Description Inventory 13.5 Practice Drills and Readiness Markers
14 Chapter 14: Final Review and Test Day
14.1 Timed Practice Strategy 14.2 Last-Week Review Map 14.3 Exam-Day Checklist 14.4 After the Exam and Next Steps
10.2 Core Concepts: Forces, Energy, and Simple Machines
Key Takeaways Explain This Topic AI
Memorize the core formulas: F = ma, W = mg, KE = ½mv², PE = mgh, work = F×d, P = W/t, V = IR.
g at Earth's surface is 9.8 m/s² (about 32 ft/s²); the Moon's is 1.62 m/s².
The six simple machines (lever, wheel-and-axle, pulley, inclined plane, wedge, screw) trade distance for force; mechanical advantage = output force / input force.
SI units: newton (force), joule (energy/work), watt (power), pascal (pressure).
Last updated: June 2026
10.2 Core Concepts: Forces, Energy, and Simple Machines
The "force relationships, physical laws, simple machines" core of Physical Science is mostly mechanics. Master a short list of formulas and you can answer the bulk of the subtest in seconds.
Newton's three laws
First Law (inertia): an object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless a net external force acts on it.
Second Law: F = ma — net force equals mass times acceleration. Rearranged, a = F/m. A larger mass needs more force for the same acceleration.
Third Law: for every action there is an equal and opposite reaction . A rocket pushes exhaust down; the exhaust pushes the rocket up.
Weight vs mass is a classic trap. Mass (kilograms) is the amount of matter and never changes. Weight is a force, W = mg , and changes with gravity. An 80-kg airman weighs about 784 N on Earth (80 × 9.8) but only ~130 N on the Moon (80 × 1.62).
Energy, work, and power
- Quantity Formula SI unit
- Force F = ma newton (N = kg·m/s²)
- Work / energy W = F × d joule (J = N·m)
- Kinetic energy KE = ½mv² joule
- Potential energy PE = mgh joule
- Power P = W / t watt (W = J/s)
- Pressure P = F / A pascal (Pa = N/m²)
The law of conservation of energy says energy is neither created nor destroyed, only transformed. A falling object trades gravitational PE for KE; a moving aircraft trading altitude for airspeed in a dive is the same exchange. Note that KE depends on velocity squared — doubling speed quadruples kinetic energy, which is why high-speed collisions are so destructive.
The six simple machines
Simple machines change the size or direction of a force; they trade distance for force but never reduce total work (ignoring friction). Mechanical advantage (MA) = output force ÷ input force.
Lever — a bar pivoting on a fulcrum; a seesaw or crowbar. Longer effort arm = greater MA.
Wheel and axle — a steering wheel or doorknob; a large wheel turns a small axle.
Pulley — redirects force; multiple pulleys multiply MA.
Inclined plane — a ramp; reduces force needed by increasing distance.
Wedge — two inclined planes back-to-back; an axe or knife.
Screw — an inclined plane wrapped around a cylinder; trades many turns for great force.
Worked example
A 50-N force lifts a load using a pulley system that requires pulling 4 m of rope to raise the load 1 m. What is the mechanical advantage? The rope distance is 4 times the load distance, so MA ≈ 4, meaning the system can lift a load up to ~200 N (50 × 4), minus friction losses.
Common traps
Confusing mass (kg) with weight (N) .
Forgetting that g = 9.8 m/s² on Earth but only 1.62 m/s² on the Moon.
Mixing units — a joule is N·m (energy), a watt is J/s (power); they are not interchangeable.
Assuming a simple machine reduces total work — it only reduces the force by spreading it over more distance.
Momentum, friction, and circular motion
Beyond the headline formulas, a few secondary mechanics ideas show up. Momentum is mass times velocity (p = mv) and is conserved in collisions — a heavy, slow truck can carry the same momentum as a light, fast car. Friction is a force that opposes motion; it converts kinetic energy into heat, which is why brakes get hot. Static friction (before sliding starts) is generally larger than kinetic friction (while sliding). Centripetal force points toward the center of a circular path and keeps an object turning rather than flying off in a straight line; a banking aircraft and a car rounding a curve both rely on it.
Speed, velocity, and acceleration
The AFOQT distinguishes scalar and vector quantities. Speed is how fast (a scalar — magnitude only); velocity adds direction (a vector). Acceleration is any change in velocity — speeding up, slowing down, or turning. Average speed = distance ÷ time, so an aircraft covering 600 miles in 1.5 hours averages 400 mph. A worked one-step item: a car starts at rest and reaches 20 m/s in 4 seconds; what is its acceleration? a = Δv/t = 20/4 = 5 m/s² . Recognizing that "starts from rest" means initial velocity is zero is half the battle on these stems.
Pressure and buoyancy
Pressure is force spread over area (P = F/A); a sharp knife cuts because a small edge area concentrates force into high pressure. Archimedes' principle says a submerged object feels an upward buoyant force equal to the weight of the fluid it displaces — objects less dense than the fluid float, denser ones sink. This connects to flight: an aircraft generates lift through pressure differences (Bernoulli's principle — faster air over the curved wing top creates lower pressure than the slower air below), which is why understanding pressure pays off across both Physical Science and Aviation Information items.