ACT Science vocabulary: physics, energy and motion.
20 terms the ACT Science section expects you to already know when a passage turns to physics, energy and motion — each with a definition, an example sentence, and a memory cue.
ACT Science does not test whether you can define these words — it tests whether you can read a figure fast enough, and an unfamiliar term is what stops you. The section gives you well under a minute per question, so the goal here is recognition, not recall: you want to meet these terms in a question stem and know immediately what they point to.
Read the definition, then the example, then the memory cue. Come back a few days later and cover the definitions — recalling a term cold is what fixes it, and rereading it is not.
The 20 terms
Alphabetical. Everything in the Physics, Energy & Motion guide.
01
acceleratedadjective
happening at a faster rate
The accelerated program finished early, helping observers compare the actual pace with what they had originally expected.
Memory cueAn accelerated arrow climbs from normal speed to a faster rate.
02
accelerationnoun
The rate at which velocity changes over time.
The falling object's acceleration remained nearly constant while its downward velocity increased each second.
Memory cueAcceleration tracks how quickly the velocity arrow changes length or direction.
03
amplifyverb
to increase in strength, size, or importance
The microphone was used to amplify the speaker's voice, helping the audience recognize how much of the larger subject it represented.
Memory cueAn amplifier turns a quiet note into a room-shaking sound, increasing its strength.
04
attenuationnoun
The process of reducing the force, effect, or value of something; weakening
The attenuation of the radio signal at greater distances limited the probe's ability to transmit data back to Earth.
Memory cueAttenuation turns a strong signal’s thick line progressively thinner and weaker.
05
forcenoun
A push or pull that can change an object's motion or shape.
A greater net force produced a larger acceleration when the cart's mass remained unchanged.
Memory cuePicture a hand pushing an arrow into an object; that push is force.
06
gravitationaladjective
Relating to the force of attraction between masses
The gravitational pull of Jupiter shields the inner planets from many asteroids that might otherwise strike Earth.
Memory cueGravitational force pulls masses toward one another across space.
07
inducedadjective/verb
Brought about or stimulated; (in this context) traffic generated as a result of new road capacity
The new highway lanes, rather than reducing congestion, induced additional traffic that quickly filled the expanded road.
Memory cueAn induced effect is brought about by a particular stimulus or change.
08
infraredadjective
Relating to electromagnetic radiation with wavelengths longer than visible light, perceived as heat
Infrared telescopes can detect heat signatures from celestial objects invisible to optical instruments.
Memory cueInfrared lies just beyond visible red and is commonly sensed as heat.
09
inhibitverb
to hinder or restrain an action
Fear can inhibit creative thinking, setting in motion a chain of events that changed what happened afterward.
Memory cueA tight brake inhibits motion by restraining it.
10
intensificationnoun
The act of making something stronger or more extreme
The intensification of the conflict along the border prompted the United Nations to deploy additional peacekeepers.
Memory cueIntensification turns the volume upward, making something stronger or more extreme.
11
magnifyverb
To increase the apparent size or importance of
The media's tendency to magnify minor disagreements into full-blown crises distorts the public's understanding of politics.
Memory cueA magnifying lens makes an object appear larger and more important.
12
momentumnoun
A quantity of motion equal to an object's mass multiplied by its velocity.
The heavier cart had greater momentum than the lighter cart moving at the same velocity.
Memory cueMomentum combines moving speed with mass, so a heavy fast object is hardest to stop.
13
oscillateverb
To move or swing back and forth; to waver between extremes
Public opinion seemed to oscillate between support for and opposition to the policy.
Memory cueA pendulum oscillates in a regular back-and-forth path.
14
paralleladjective
similar or corresponding
The parallel stories shared common themes, giving observers a more precise basis for comparing the two subjects.
Memory cueParallel lines travel side by side like similar, corresponding ideas.
15
potentadjective
powerful; having a strong effect.
Even a small dose of the potent medication produced a measurable change in heart rate.
Memory cueA potent drop creates a powerful effect far larger than itself.
16
propagateverb
to spread and promote widely
The internet helped propagate the idea, setting in motion a chain of events that changed what happened afterward.
Memory cuePropagate an idea by sending copies outward through many channels.
17
staticadjective
not moving or changing; stationary; can also mean noise in a radio/TV.
Wages remained static for years, clarifying the kind and degree of activity taking place in the situation.
Memory cueA static object remains frozen; radio static crackles without a clear signal.
18
stimulatedverb
encouraged or aroused interest or enthusiasm; increased activity in
The discussion stimulated new ideas among the team members, producing consequences that became increasingly apparent as the situation continued to develop.
Memory cueA spark stimulated the engine, raising both activity and interest.
19
velocitynoun
The rate at which an object's position changes in a specified direction.
The cart's velocity became negative after it reversed direction and rolled back toward the sensor.
Memory cueVelocity is speed wearing a direction arrow; both size and direction matter.
20
wavelengthnoun
The distance between matching points on successive cycles of a wave.
The diagram shows wavelength as the horizontal distance from one wave crest to the next.
Memory cueWavelength is the ruler laid from one wave crest to its matching neighbor.
Knowing the words is step one — reading the figure is step two.
Test Ninjas puts these terms back into real Science passages — full-length ACT practice tests, a complete Science course, and an explanation on every question.
