AP Physics 1: 250 Concepts, Relationships and Limits

Knowing conservation of energy is not the same as knowing when it does not hold.

250 cardsLast updated 2026-08-31

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A student who can write conservation of mechanical energy still gets the wrong answer on a rough incline. A student who knows the momentum principle still misapplies it when a pivot supplies an external force. Physics rewards knowing a relationship and its conditions together, and most lost marks come from applying a correct equation in a situation it was never valid for. This deck is 250 cards, one quantity, law or concept per card, with the back cut into three fixed lines. "Meaning" says what the quantity or law states in a sentence. "Detail" gives the relationship in words and symbols and the condition under which it holds. "Watch for" names the quantity it is confused with or the case where it fails. The sections follow the course: kinematics, forces and Newton's laws, work, energy and power, momentum and collisions, rotation and gravitation, and oscillations, waves and circuits. No worked numbers appear. Relationships are written inline as sentences, because the exam rewards reasoning stated in words at least as much as a computed value. Once the deck is on a spaced-repetition schedule, the relationships you can already place stop coming back and the pairs you keep reversing return until they stop being guesswork.

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Showing 100 representative cards from the full 250-card deck.

Front	Back
Position	Meaning: The location of an object relative to a chosen origin. Detail: Written as x and measured along a chosen axis, so its sign depends on the direction you call positive. Watch for: Position is not distance travelled. An object can return to its starting position after moving a long way.
Distance travelled	Meaning: The total path length covered by an object. Detail: It is a scalar and is never negative. Watch for: It equals the size of the displacement only when the motion does not reverse direction.
Average speed	Meaning: Total distance travelled divided by total time. Detail: A scalar quantity with no direction. Watch for: It differs from the size of the average velocity whenever the path is not a straight line in one direction.
Acceleration	Meaning: The rate at which velocity changes with time. Detail: Equal to change in velocity over change in time, and directed along the change in velocity. Watch for: An object can have zero velocity and nonzero acceleration, as at the top of a vertical throw.
Position-time graph	Meaning: A graph of position against time. Detail: Its slope gives velocity, and curvature indicates acceleration. Watch for: The area under a position-time graph has no physical meaning.
Reading area from a graph	Meaning: Finding a physical quantity as the area under a curve. Detail: Split the region into triangles and rectangles and add the signed areas. Watch for: Areas below the axis must be subtracted, not added as positive amounts.
Constant acceleration	Meaning: Motion in which velocity changes at a steady rate. Detail: The velocity-time graph is a straight line and the position-time graph is a parabola. Watch for: The kinematic equations apply only when acceleration is constant.
Time-independent relationship	Meaning: A relationship linking velocities, acceleration and displacement without time. Detail: Final velocity squared equals initial velocity squared plus twice acceleration times displacement. Watch for: Taking the square root introduces two possible signs, and the context decides which applies.
Free fall	Meaning: Motion under the influence of gravity alone. Detail: The acceleration is directed downward and has the same size for every object. Watch for: Air resistance is neglected. Real falling objects reach a terminal speed.
Object thrown upward	Meaning: An object launched vertically and then falling back. Detail: At the highest point the velocity is zero but the acceleration is not. Watch for: Assuming zero acceleration at the top is a common and costly error.
Projectile motion	Meaning: Motion of an object launched into the air and moving under gravity alone. Detail: The horizontal and vertical motions are independent and share only the time. Watch for: Gravity does not affect the horizontal velocity, which stays constant.
Time of flight	Meaning: How long a projectile stays in the air. Detail: It is determined entirely by the vertical motion and the launch height. Watch for: Launching faster horizontally does not keep a projectile in the air longer.
Velocity at the top of a trajectory	Meaning: The velocity of a projectile at its highest point. Detail: The vertical component is zero while the horizontal component is unchanged. Watch for: The total velocity is not zero unless the launch was purely vertical.
Relative velocity	Meaning: The velocity of one object as measured in the frame of another. Detail: Found by subtracting the velocity of the observer from the velocity of the object. Watch for: The order of subtraction matters and reversing it reverses the direction.
Force	Meaning: A push or a pull that one object exerts on another. Detail: It is a vector measured in newtons, and it always involves two objects. Watch for: A force is an interaction, not something an object possesses or carries with it.
Inertia	Meaning: The tendency of an object to resist changes in its motion. Detail: It is measured by mass, so a heavier object is harder to accelerate. Watch for: Inertia is not a force and does not appear on a free-body diagram.
Free-body diagram	Meaning: A diagram showing all forces acting on a single object. Detail: Each force is drawn as an arrow from the object, labelled by type and source. Watch for: Never include forces the object exerts on other things, and never include acceleration as a force.
Newton's first law	Meaning: An object at rest stays at rest and an object in motion continues at constant velocity unless a net force acts. Detail: It defines what an inertial reference frame is. Watch for: It does not say that no forces act, only that they cancel.
Newton's third law	Meaning: When one object exerts a force on a second, the second exerts an equal and opposite force on the first. Detail: The two forces act on different objects and are of the same type. Watch for: Because they act on different objects, they never cancel each other in one free-body diagram.
Weight	Meaning: The gravitational force exerted on an object. Detail: Equal to mass times the gravitational field strength and always directed downward. Watch for: Weight changes on another planet even though the mass does not.
Normal force on an incline	Meaning: The perpendicular support force on a sloped surface. Detail: It balances only the component of weight perpendicular to the surface. Watch for: It is smaller than the weight, and it decreases as the incline gets steeper.
Static friction	Meaning: The force that prevents surfaces from sliding relative to each other. Detail: It takes whatever value is needed up to a maximum set by the coefficient times the normal force. Watch for: Using the maximum value when the object is not on the verge of slipping is wrong.
Coefficient of friction	Meaning: A number describing how rough a pair of surfaces is. Detail: It has no units and depends on both materials in contact. Watch for: It does not depend on the contact area or on the speed in the simple model.
Tension	Meaning: The pulling force transmitted along a string, rope or cable. Detail: It is the same throughout an ideal massless string over a frictionless pulley. Watch for: Tension pulls and never pushes, so its direction is always away from the object along the string.
Connected objects	Meaning: Two or more objects joined so that they move together. Detail: They share the same size of acceleration, and the connecting force appears in both equations. Watch for: Treating the system as one object gives the acceleration but hides the tension.
Spring force	Meaning: The restoring force exerted by a stretched or compressed spring. Detail: Its size is the spring constant times the displacement from the natural length. Watch for: It is measured from the natural length, not from any convenient starting position.
Equilibrium	Meaning: The condition in which the net force on an object is zero. Detail: The object is then at rest or moving with constant velocity. Watch for: Equilibrium does not require the object to be at rest.
Forces on an incline	Meaning: The forces acting on an object resting on a slope. Detail: Weight, normal force and friction act, and the weight resolves into components along and perpendicular to the surface. Watch for: The component along the surface uses the sine of the angle, not the cosine.
Systems of objects	Meaning: A group of objects analysed together. Detail: Internal forces cancel within the system, leaving only external forces. Watch for: Tension between two blocks is internal to the pair but external to each block alone.
Force versus acceleration graph	Meaning: A graph relating net force to acceleration for an object. Detail: Its slope gives the mass of the object. Watch for: The slope is the mass itself, not its reciprocal.
Two blocks in contact	Meaning: Two blocks pushed together across a surface. Detail: They share an acceleration, and the contact force between them follows from applying the second law to one block. Watch for: The contact force is not equal to the applied force unless the second block has all the mass.
Air resistance	Meaning: A drag force opposing motion through a fluid. Detail: It grows with speed, so acceleration decreases as an object falls faster. Watch for: It is usually ignored in problems, and that assumption should be stated.
Work	Meaning: The energy transferred to an object by a force acting through a displacement. Detail: It equals the force times the displacement times the cosine of the angle between them. Watch for: A force with no displacement does no work, however hard it is applied.
Work by a variable force	Meaning: Work done when the force changes during the displacement. Detail: It equals the area under a graph of force against position. Watch for: Multiplying the maximum force by the distance overestimates the work.
Kinetic energy	Meaning: The energy an object has because of its motion. Detail: It equals one half the mass times the speed squared. Watch for: It is a scalar and is never negative, whatever the direction of motion.
Elastic potential energy	Meaning: The energy stored in a stretched or compressed spring. Detail: It equals one half the spring constant times the square of the displacement from the natural length. Watch for: It is positive for both stretching and compression because the displacement is squared.
Work-energy theorem	Meaning: The statement that the net work done on an object equals its change in kinetic energy. Detail: It links forces acting over a distance directly to a change in speed. Watch for: It uses the net work, so the work of every force must be included.
Conservative force	Meaning: A force whose work depends only on the endpoints of the motion. Detail: Gravity and the spring force are conservative, and each has an associated potential energy. Watch for: A conservative force does zero net work around any closed path.
Conservation of energy	Meaning: The principle that the total energy of an isolated system does not change. Detail: Energy may change form but the total stays constant. Watch for: Energy can leave a system as heat or sound, so the system boundary must be stated.
Energy bar chart	Meaning: A diagram comparing the forms of energy at two moments. Detail: Bars for the initial state plus energy added must equal bars for the final state. Watch for: A missing internal energy bar is the usual reason a chart fails to balance.
Energy at the bottom of a swing	Meaning: The energy of a pendulum at its lowest point. Detail: All the gravitational potential energy relative to that point has become kinetic energy. Watch for: The speed there does not depend on the mass of the bob.
Power	Meaning: The rate at which work is done or energy is transferred. Detail: It equals work divided by time, measured in watts. Watch for: Power is not energy. A small motor can do the same work as a large one, given more time.
Average power	Meaning: Total energy transferred divided by the total time. Detail: Useful when the rate varies during the process. Watch for: It is not the average of the initial and final instantaneous powers.
Dissipative force	Meaning: A force that converts mechanical energy into internal energy. Detail: Friction and air resistance are the common examples. Watch for: The energy is not destroyed. It is spread among many particles.
Energy in a spring launcher	Meaning: A compressed spring accelerating an object. Detail: The stored elastic energy becomes kinetic energy when the spring returns to its natural length. Watch for: The launch speed depends on the square root of the stored energy, not on it directly.
Force-position graph	Meaning: A graph of the force applied against the position of the object. Detail: The area beneath the curve gives the work done. Watch for: Area below the axis represents negative work and must be subtracted.
Energy transfer versus energy transformation	Meaning: Energy moving between objects and energy changing form. Detail: Work and heat transfer energy across a boundary, while conversion changes its form inside. Watch for: The two ideas are different and the wording of a question usually signals which is meant.
Turning point	Meaning: A position where an object momentarily stops and reverses. Detail: It occurs where the total energy equals the potential energy. Watch for: The force there is not zero, which is why the object turns around.
Momentum	Meaning: The product of an object's mass and its velocity. Detail: It is a vector pointing in the direction of the velocity, measured in kilogram metres per second. Watch for: Momentum is not energy. Two objects can share a momentum and have very different kinetic energies.
Impulse	Meaning: The product of a force and the time interval over which it acts. Detail: It equals the change in momentum of the object, measured in newton seconds. Watch for: A small force over a long time can give the same impulse as a large force over a short one.
Impulse from a graph	Meaning: Finding the impulse when the force varies with time. Detail: It equals the area under a graph of force against time. Watch for: Multiplying the peak force by the duration overestimates the impulse.
Why airbags work	Meaning: The physical reason for cushioning devices. Detail: They increase the time over which momentum changes, lowering the average force. Watch for: They do not reduce the change in momentum, only the force needed to produce it.
Isolated system	Meaning: A system on which no net external force acts. Detail: Internal forces come in third-law pairs and cancel in the total. Watch for: A system can be isolated in one direction and not in another, which is often enough.
Elastic collision	Meaning: A collision in which total kinetic energy is conserved. Detail: Both momentum and kinetic energy equations can be written. Watch for: Perfectly elastic collisions are an idealisation except at the atomic scale.
Perfectly inelastic collision	Meaning: A collision in which the objects stick together. Detail: They share a common final velocity found from conservation of momentum. Watch for: This case loses the most kinetic energy, but not all of it unless the total momentum is zero.
Recoil	Meaning: The backward motion of an object that expels another. Detail: The momenta of the two are equal in size and opposite in direction if the system started at rest. Watch for: The recoil speed is smaller for the more massive object, but the momenta match.
Glancing collision	Meaning: A collision in which the objects move off at angles. Detail: Momentum must be conserved along two perpendicular axes. Watch for: The final directions cannot be found from momentum alone without more information.
Centre of mass	Meaning: The point at which the mass of a system can be considered concentrated. Detail: It is the mass-weighted average of the positions of the parts. Watch for: It need not lie within any of the objects, as with a ring.
Centre of mass in an explosion	Meaning: The behaviour of the centre of mass when a body breaks apart. Detail: It continues along the original trajectory as if nothing had happened. Watch for: The pieces scatter, but their weighted average position does not deviate.
Choosing momentum or energy	Meaning: Deciding which conservation law to apply. Detail: Use momentum for collisions and explosions, and energy for motion through heights or springs. Watch for: Both apply during an elastic collision, and using only one leaves the problem underdetermined.
Collisions with a wall	Meaning: An object bouncing off a fixed surface. Detail: The momentum change is largest when the object rebounds rather than sticking. Watch for: Momentum is not conserved for the object alone, because the wall exerts an external force.
Impulse in a bouncing collision	Meaning: The impulse delivered when an object rebounds. Detail: The momentum change includes a reversal of direction, so it exceeds the initial momentum. Watch for: Subtracting the speeds instead of accounting for the sign change halves the correct answer.
Comparing collisions by energy	Meaning: Classifying a collision from the kinetic energies before and after. Detail: Compare the totals. Equal means elastic, less means inelastic. Watch for: A collision cannot end with more kinetic energy unless stored energy was released.
Angular position	Meaning: The angle locating a rotating object relative to a reference direction. Detail: Measured in radians, where a full turn is two pi radians. Watch for: Degrees must be converted to radians before rotational relationships are used.
Angular acceleration	Meaning: The rate at which angular velocity changes. Detail: Measured in radians per second squared and produced by a net torque. Watch for: It is zero for uniform circular motion even though the linear acceleration is not.
Centripetal acceleration	Meaning: The acceleration directed toward the centre of a circular path. Detail: It equals the speed squared divided by the radius, or the radius times the angular speed squared. Watch for: It exists even at constant speed, because the direction of velocity keeps changing.
Vertical circular motion	Meaning: Circular motion in a vertical plane, as on a loop. Detail: At the top, gravity and the normal force both point toward the centre. Watch for: The minimum speed at the top is where the normal force reaches zero, not where the speed is zero.
Torque	Meaning: The turning effect of a force about an axis. Detail: It equals the force times the perpendicular distance from the axis to the line of the force. Watch for: A force through the axis produces no torque however large it is.
Sign of torque	Meaning: Whether a torque tends to turn an object one way or the other. Detail: One sense of rotation is chosen as positive and the other becomes negative. Watch for: The sign convention must be fixed before torques are summed.
Rotational inertia	Meaning: The resistance of an object to angular acceleration. Detail: It depends on the mass and on how that mass is distributed about the axis. Watch for: It is not a fixed property of an object. It changes when the axis changes.
Comparing common shapes	Meaning: How rotational inertia differs among simple bodies of equal mass and radius. Detail: A hoop has more than a disc, which has more than a sphere. Watch for: Mass concentrated near the rim always gives a larger value.
Rotational form of the second law	Meaning: The relationship between net torque and angular acceleration. Detail: Net torque equals rotational inertia times angular acceleration. Watch for: The rotational inertia takes the role of mass, and it is not the same as mass.
Rolling without slipping	Meaning: Motion in which the contact point does not slide. Detail: The speed of the centre equals the radius times the angular speed. Watch for: Static friction acts at the contact point and does no work in this case.
Angular momentum	Meaning: The rotational analogue of linear momentum. Detail: For a rigid body it equals the rotational inertia times the angular velocity. Watch for: It depends on the axis chosen, so the axis must be stated.
Conservation of angular momentum	Meaning: The principle that angular momentum is constant when no net external torque acts. Detail: It explains why a spinning skater speeds up when the arms are pulled in. Watch for: It is a separate law from conservation of linear momentum, and one can hold while the other fails.
Angular impulse	Meaning: The product of torque and the time over which it acts. Detail: It equals the change in angular momentum. Watch for: It is the rotational counterpart of impulse and follows the same reasoning.
Static equilibrium conditions	Meaning: The two requirements for an object to remain at rest. Detail: The net force and the net torque must both be zero. Watch for: Satisfying only one condition is not enough.
Newton's law of universal gravitation	Meaning: The statement that every mass attracts every other mass. Detail: The force is proportional to the product of the masses and inversely proportional to the square of the distance. Watch for: The distance is measured between centres, not between surfaces.
Gravitational field strength	Meaning: The gravitational force per unit mass at a point. Detail: It equals the gravitational constant times the source mass divided by the square of the distance. Watch for: It is a property of the field, so it does not depend on the test mass.
Orbital motion	Meaning: The motion of a satellite held in a circular path by gravity. Detail: Gravity supplies exactly the centripetal force required. Watch for: A satellite in orbit is in free fall, not weightless because gravity has vanished.
Orbital period	Meaning: The time a satellite takes to complete one orbit. Detail: Its square is proportional to the cube of the orbital radius. Watch for: Doubling the radius more than doubles the period.
Apparent weightlessness	Meaning: The sensation experienced by an orbiting astronaut. Detail: The astronaut and the spacecraft fall together, so the normal force is zero. Watch for: Gravity is still acting, and it is what keeps them in orbit.
Gravitational potential energy at large distances	Meaning: The stored energy of two masses separated by a large distance. Detail: It is taken as negative and approaches zero as the separation grows without limit. Watch for: The simple product of weight and height applies only near a surface.
Simple harmonic motion	Meaning: Oscillation in which the restoring force is proportional to the displacement and opposite to it. Detail: The resulting position varies as a sine or cosine of time. Watch for: Not every oscillation is simple harmonic. The proportionality must hold.
Amplitude	Meaning: The greatest displacement from equilibrium during an oscillation. Detail: It sets the total energy of the oscillator. Watch for: It does not affect the period of an ideal mass-spring system or a small-angle pendulum.
Frequency	Meaning: The number of complete cycles per second. Detail: Measured in hertz. Watch for: Angular frequency is two pi times this value, and the two must not be interchanged.
Energy in simple harmonic motion	Meaning: The exchange between kinetic and potential energy during oscillation. Detail: Total energy stays constant and is proportional to the square of the amplitude. Watch for: Kinetic energy is greatest at equilibrium, not at the extremes.
Simple pendulum	Meaning: A mass swinging on a light string. Detail: For small angles its period depends on the length and the gravitational field strength. Watch for: The period does not depend on the mass of the bob.
Pendulum on another planet	Meaning: How the period changes with gravitational field strength. Detail: A weaker field gives a longer period. Watch for: Changing the mass of the bob has no effect.
Mechanical wave	Meaning: A disturbance that travels through a medium carrying energy. Detail: The medium oscillates about fixed positions while the disturbance moves. Watch for: The medium itself is not transported along with the wave.
Wavelength	Meaning: The distance between successive identical points on a wave. Detail: Measured from crest to crest or compression to compression. Watch for: It is a distance in space, not a time.
Superposition	Meaning: The principle that overlapping waves add displacement by displacement. Detail: The resulting displacement is the sum of the individual displacements at each point. Watch for: The waves pass through each other unchanged after overlapping.
Standing wave	Meaning: A pattern formed when two identical waves travel in opposite directions. Detail: It has fixed nodes and antinodes and does not transport energy along the medium. Watch for: It is not a wave moving very slowly. Nothing propagates.
Fundamental frequency	Meaning: The lowest frequency at which a standing wave forms. Detail: It corresponds to the longest possible wavelength for the system. Watch for: Higher harmonics are whole-number multiples of it only for a string or an open pipe.
Sound as a wave	Meaning: A longitudinal pressure wave travelling through a medium. Detail: Its speed depends on the medium and increases with temperature in air. Watch for: Sound cannot travel through a vacuum.
Electric charge	Meaning: A property of matter that produces electrical forces. Detail: It comes in two signs and is measured in coulombs. Watch for: Charge is conserved. It is transferred, never created.
Resistance	Meaning: The opposition a component offers to current. Detail: Measured in ohms, equal to the potential difference divided by the current. Watch for: It is a property of the component, not of the circuit it sits in.
Adding resistors in parallel	Meaning: Finding the combined resistance of parallel branches. Detail: The reciprocals of the resistances add to give the reciprocal of the total. Watch for: Forgetting the final reciprocal is a common and large error.
Electrical power	Meaning: The rate at which electrical energy is transferred. Detail: It equals current times potential difference, measured in watts. Watch for: The forms using resistance follow from Ohm's law and apply only to ohmic components.
Ammeter and voltmeter	Meaning: Instruments for measuring current and potential difference. Detail: An ammeter goes in series and a voltmeter in parallel. Watch for: Connecting an ammeter in parallel across a supply short circuits it.

Frequently asked

What is in each section of the deck?

Kinematics has 35 cards, forces and Newton's laws 45, work, energy and power 40, momentum and collisions 35, rotation and gravitation 45, and oscillations, waves and circuits 50, for 250 in total. Every card carries section and subtopic tags, so you can drill only rotation, only circuits, or only energy.

Are there worked calculations?

No. Cards describe relationships in words and symbols rather than substituting numbers. The reason is that the hard part of a physics problem is choosing which principle applies and checking its conditions, and that choice is made before any arithmetic starts. Numerical practice still has to happen on problem sets.

Does it cover the qualitative reasoning questions?

Directly. The exam asks students to explain why something happens and to justify a claim with physics principles, and the third line on every card names the misconception those questions are usually built around. Writing full paragraph answers is still separate practice.

Can I import the whole deck on the free plan?

Yes. Importing a saved deck runs no new AI generation and spends no AI credits, so the free plan imports all 250 cards. You can study, edit and delete them afterwards.

Will importing it twice create duplicates?

No. Cards you already have are skipped and only cards added in a revision come through. Including re-imports after deleting it, one official deck can be imported three times per account.

Can I use it on the web and in the mobile app?

Yes. The deck is added to your account rather than to a device, so the same cards and the same progress are there on the web, on iOS and on Android.

Can I edit the cards after importing?

Yes. Imported cards are yours: you can edit both sides, delete cards you do not need, change tags, and move cards to another deck.