Science Glossary
Plain-English physics terms with formulas and units—then jump into density, pressure, Ohm's law, and motion calculators.
8 terms · Linked from popular calculators on the hub
Categories
Ohm's law
ElectricityDefinition
Relates voltage (V), current (I), and resistance (R) in a simple circuit: V = I × R.
Formula
V = I R · I = V/R · R = V/IExample
**12 V** across **4 Ω** → current **3 A**. Power dissipated P = VI = **36 W**.
Why it matters
Circuit debugging and component sizing start with Ohm's law.
Common mistakes
- ✗Mixing mA with A without converting
- ✗Applying Ohm's law to non-ohmic devices without caution
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Density
Mechanics & fluidsDefinition
Mass per unit volume—how heavy a material is for its size.
Formula
ρ = m / VExample
Mass **2 kg**, volume **0.001 m³** → ρ = **2000 kg/m³** (near water).
Why it matters
Buoyancy, material selection, and pressure problems use density.
Common mistakes
- ✗Using g/cm³ and kg/m³ interchangeably without ×1000 conversion
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Pressure
Mechanics & fluidsDefinition
Force per unit area acting perpendicular to a surface.
Formula
P = F / AExample
Force **500 N** on **0.25 m²** → P = **2000 Pa** (about 0.29 psi).
Why it matters
Hydraulics, weather, and diving tables are pressure problems.
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Speed & velocity
KinematicsDefinition
Speed is distance per time; velocity adds direction. Average speed = total distance ÷ time.
Formula
v = d / tExample
**180 km** in **2 h** → average speed **90 km/h**.
Why it matters
Motion problems chain into acceleration and force (Newton's laws).
Common mistakes
- ✗Using km/h in formulas that expect m/s without converting
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Force (Newton's laws)
KinematicsDefinition
Push or pull that changes motion. Newton's 2nd law: net force equals mass times acceleration.
Formula
F = m aExample
**10 kg** at **2 m/s²** → net force **20 N**.
Why it matters
Dynamics, friction, and inclined-plane problems all start with F = ma.
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Power & energy
EnergyDefinition
Power is energy per time (watts = joules per second). Electrical power P = VI.
Formula
P = E/t · P = V IExample
**120 V**, **2 A** → **240 W**. Run **1 hour** → energy **0.24 kWh**.
Why it matters
Links mechanics and electricity—motors, heaters, and grid costs.
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Heat index & wind chill
ThermodynamicsDefinition
Heat index estimates perceived temperature with humidity; wind chill estimates perceived cold with wind—both differ from thermometer readings.
Why it matters
Safety planning for outdoor work, sports, and travel.
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Energy in collisions
RelativityDefinition
In classical physics, kinetic energy is ½mv²; relativistic systems add rest mass energy (E = mc²). Collision calculators compare before/after momentum and energy.
Why it matters
Extreme astrophysics and particle physics need relativistic energy—not just ½mv².
Common mistakes
- ✗Using non-relativistic KE for speeds near the speed of light
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