Physics & Mechanics
Newton's laws, energy, waves, and heat transfer are the physics core of GS, the test rewards knowing the right formula and applying it cleanly.
Formula Reference
- Newton's 2nd Law: F = ma (force in Newtons, mass in kg, acceleration in m/s²)
- Work: W = F × d (force times distance, units: Joules)
- Power: P = W/t (work divided by time, units: Watts)
- Kinetic energy: KE = ½mv² (mass in kg, velocity in m/s)
- Potential energy: PE = mgh (mass × gravitational acceleration × height)
- Wave speed: v = f × λ (frequency × wavelength)
- Heat transfer: conduction (direct contact), convection (fluid movement), radiation (electromagnetic waves)
What the ASVAB is actually testing
Physics questions on GS test four areas: Newton's laws of motion, energy and work, waves and sound, and heat transfer. You don't need calculus, you need the right formula, clean substitution, and a solid understanding of the vocabulary. Most physics questions give you two numbers and ask for a third.
Newton's three laws
Net force = ΣF. Object accelerates in the direction of the unbalanced force.
- 1st Law (Inertia): An object at rest stays at rest; an object in motion stays in motion, unless acted on by a net external force. This is why you lurch forward when a vehicle brakes.
- 2nd Law: F = ma. Net force equals mass times acceleration. Bigger mass means more force required to produce the same acceleration.
- 3rd Law: Every action has an equal and opposite reaction. When you fire a weapon, the recoil is the reaction force.
Work, energy, and power
Work only happens when a force causes displacement in the direction of the force. Holding a weight overhead involves force, but if you're not moving it, you're doing zero mechanical work.
Energy comes in two key forms:
- Kinetic energy (KE): energy of motion, KE = ½mv². Double the speed, quadruple the kinetic energy.
- Potential energy (PE): stored energy, PE = mgh. Taller position, more potential energy.
Power is the rate of doing work. A motor that does the same job in half the time is twice as powerful.
Waves
Waves transfer energy without transferring matter. Key vocabulary:
| Term | Meaning |
|---|---|
| Frequency (f) | Cycles per second (Hertz) |
| Wavelength (λ) | Distance between wave peaks |
| Amplitude | Height of the wave (intensity/loudness/brightness) |
Higher frequency = shorter wavelength (at a given speed). Sound waves are longitudinal (particles compress); light waves are transverse (electromagnetic).
Heat transfer
Heat moves in three ways:
- Conduction, direct contact (metal handle heats up)
- Convection, fluid circulation (boiling water, wind patterns)
- Radiation, electromagnetic waves through space (heat from the sun)
Study approach
Memorize the formulas in the reference block above. Practice plugging in numbers, the arithmetic on GS physics is usually simple once you have the right equation. Focus on understanding what each law describes qualitatively so you can answer concept questions without calculation.
Common Pitfalls
- ⚠Mixing up mass (kg, always constant) with weight (force due to gravity, changes by location)
- ⚠Forgetting that Newton's 1st Law applies to objects already moving, an object in motion stays in motion unless a net force acts on it
- ⚠Confusing work (requires displacement) with force, pushing on an immovable wall does zero work
- ⚠Thinking higher frequency = longer wavelength, they're inversely related at constant wave speed
- ⚠Mixing up conduction and convection, conduction is particle-to-particle contact; convection requires fluid (liquid or gas) movement
Worked Examples
Q1: A 10 kg object accelerates at 3 m/s². What net force is acting on it?
Answer: F = ma = 10 kg × 3 m/s² = 30 Newtons
Q2: A soldier does 600 J of work pushing a crate 12 meters. How much force did he apply?
Answer: W = F × d → F = W/d = 600 J ÷ 12 m = 50 Newtons
Q3: A wave has a frequency of 200 Hz and a wavelength of 2 m. What is its speed?
Answer: v = f × λ = 200 Hz × 2 m = 400 m/s