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 giving what it states and, where it applies, a line on what 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.

What happens when you add it

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The button opens Memly and the whole deck lands in your account.
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Each card gets its own schedule, based on how well you actually recall it.
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What's inside

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

Front	Back
Position — what is it?	The location of an object relative to a chosen origin. Position is not distance travelled. An object can return to its starting position after moving a long way.
Distance travelled — what is it?	The total path length covered by an object. It equals the size of the displacement only when the motion does not reverse direction.
Average speed — what is it?	Total distance travelled divided by total time. It differs from the size of the average velocity whenever the path is not a straight line in one direction.
Acceleration — what is it?	The rate at which velocity changes with time. An object can have zero velocity and nonzero acceleration, as at the top of a vertical throw.
Position-time graph — what is it?	A graph of position against time. The area under a position-time graph has no physical meaning.
Reading area from a graph — what is it?	Finding a physical quantity as the area under a curve. Areas below the axis must be subtracted, not added as positive amounts.
Constant acceleration — what is it?	Motion in which velocity changes at a steady rate. The kinematic equations apply only when acceleration is constant.
Time-independent relationship — what is it?	A relationship linking velocities, acceleration and displacement without time. Taking the square root introduces two possible signs, and the context decides which applies.
Free fall — what is it?	Motion under the influence of gravity alone. Air resistance is neglected. Real falling objects reach a terminal speed.
Object thrown upward — what is it?	An object launched vertically and then falling back. Assuming zero acceleration at the top is a common and costly error.
Projectile motion — what is it?	Motion of an object launched into the air and moving under gravity alone. Gravity does not affect the horizontal velocity, which stays constant.
Time of flight — what is it?	How long a projectile stays in the air. Launching faster horizontally does not keep a projectile in the air longer.
Velocity at the top of a trajectory — what is it?	The velocity of a projectile at its highest point. The total velocity is not zero unless the launch was purely vertical.
Relative velocity — what is it?	The velocity of one object as measured in the frame of another. The order of subtraction matters and reversing it reverses the direction.
Force — what is it?	A push or a pull that one object exerts on another. A force is an interaction, not something an object possesses or carries with it.
Inertia — what is it?	The tendency of an object to resist changes in its motion. Inertia is not a force and does not appear on a free-body diagram.
Free-body diagram — what is it?	A diagram showing all forces acting on a single object. Never include forces the object exerts on other things, and never include acceleration as a force.
Newton's first law — what is it?	An object at rest stays at rest and an object in motion continues at constant velocity unless a net force acts. It does not say that no forces act, only that they cancel.
Newton's third law — what is it?	When one object exerts a force on a second, the second exerts an equal and opposite force on the first. Because they act on different objects, they never cancel each other in one free-body diagram.
Weight — what is it?	The gravitational force exerted on an object. Weight changes on another planet even though the mass does not.
Normal force on an incline — what is it?	The perpendicular support force on a sloped surface. It is smaller than the weight, and it decreases as the incline gets steeper.
Static friction — what is it?	The force that prevents surfaces from sliding relative to each other. Using the maximum value when the object is not on the verge of slipping is wrong.
Coefficient of friction — what is it?	A number describing how rough a pair of surfaces is. It does not depend on the contact area or on the speed in the simple model.
Tension — what is it?	The pulling force transmitted along a string, rope or cable. Tension pulls and never pushes, so its direction is always away from the object along the string.
Connected objects — what is it?	Two or more objects joined so that they move together. Treating the system as one object gives the acceleration but hides the tension.
Spring force — what is it?	The restoring force exerted by a stretched or compressed spring. It is measured from the natural length, not from any convenient starting position.
Equilibrium — what is it?	The condition in which the net force on an object is zero. Equilibrium does not require the object to be at rest.
Forces on an incline — what is it?	The forces acting on an object resting on a slope. The component along the surface uses the sine of the angle, not the cosine.
Systems of objects — what is it?	A group of objects analysed together. Tension between two blocks is internal to the pair but external to each block alone.
Force versus acceleration graph — what is it?	A graph relating net force to acceleration for an object. The slope is the mass itself, not its reciprocal.
Two blocks in contact — what is it?	Two blocks pushed together across a surface. The contact force is not equal to the applied force unless the second block has all the mass.
Air resistance — what is it?	A drag force opposing motion through a fluid. It is usually ignored in problems, and that assumption should be stated.
Work — what is it?	The energy transferred to an object by a force acting through a displacement. A force with no displacement does no work, however hard it is applied.
Work by a variable force — what is it?	Work done when the force changes during the displacement. Multiplying the maximum force by the distance overestimates the work.
Kinetic energy — what is it?	The energy an object has because of its motion. It is a scalar and is never negative, whatever the direction of motion.
Elastic potential energy — what is it?	The energy stored in a stretched or compressed spring. It is positive for both stretching and compression because the displacement is squared.
Work-energy theorem — what is it?	The statement that the net work done on an object equals its change in kinetic energy. It uses the net work, so the work of every force must be included.
Conservative force — what is it?	A force whose work depends only on the endpoints of the motion. A conservative force does zero net work around any closed path.
Conservation of energy — what is it?	The principle that the total energy of an isolated system does not change. Energy can leave a system as heat or sound, so the system boundary must be stated.
Energy bar chart — what is it?	A diagram comparing the forms of energy at two moments. A missing internal energy bar is the usual reason a chart fails to balance.
Energy at the bottom of a swing — what is it?	The energy of a pendulum at its lowest point. The speed there does not depend on the mass of the bob.
Power — what is it?	The rate at which work is done or energy is transferred. Power is not energy. A small motor can do the same work as a large one, given more time.
Average power — what is it?	Total energy transferred divided by the total time. It is not the average of the initial and final instantaneous powers.
Dissipative force — what is it?	A force that converts mechanical energy into internal energy. The energy is not destroyed. It is spread among many particles.
Energy in a spring launcher — what is it?	A compressed spring accelerating an object. The launch speed depends on the square root of the stored energy, not on it directly.
Force-position graph — what is it?	A graph of the force applied against the position of the object. Area below the axis represents negative work and must be subtracted.
Energy transfer versus energy transformation — what is it?	Energy moving between objects and energy changing form. The two ideas are different and the wording of a question usually signals which is meant.
Turning point — what is it?	A position where an object momentarily stops and reverses. The force there is not zero, which is why the object turns around.
Momentum — what is it?	The product of an object's mass and its velocity. Momentum is not energy. Two objects can share a momentum and have very different kinetic energies.
Impulse — what is it?	The product of a force and the time interval over which it acts. A small force over a long time can give the same impulse as a large force over a short one.
Impulse from a graph — what is it?	Finding the impulse when the force varies with time. Multiplying the peak force by the duration overestimates the impulse.
Why airbags work — can you explain it?	The physical reason for cushioning devices. They do not reduce the change in momentum, only the force needed to produce it.
Isolated system — what is it?	A system on which no net external force acts. A system can be isolated in one direction and not in another, which is often enough.
Elastic collision — what is it?	A collision in which total kinetic energy is conserved. Perfectly elastic collisions are an idealisation except at the atomic scale.
Perfectly inelastic collision — what is it?	A collision in which the objects stick together. This case loses the most kinetic energy, but not all of it unless the total momentum is zero.
Recoil — what is it?	The backward motion of an object that expels another. The recoil speed is smaller for the more massive object, but the momenta match.
Glancing collision — what is it?	A collision in which the objects move off at angles. The final directions cannot be found from momentum alone without more information.
Centre of mass — what is it?	The point at which the mass of a system can be considered concentrated. It need not lie within any of the objects, as with a ring.
Centre of mass in an explosion — what is it?	The behaviour of the centre of mass when a body breaks apart. The pieces scatter, but their weighted average position does not deviate.
Choosing momentum or energy — what is it?	Deciding which conservation law to apply. Both apply during an elastic collision, and using only one leaves the problem underdetermined.
Collisions with a wall — what is it?	An object bouncing off a fixed surface. Momentum is not conserved for the object alone, because the wall exerts an external force.
Impulse in a bouncing collision — what is it?	The impulse delivered when an object rebounds. Subtracting the speeds instead of accounting for the sign change halves the correct answer.
Comparing collisions by energy — what is it?	Classifying a collision from the kinetic energies before and after. A collision cannot end with more kinetic energy unless stored energy was released.
Angular position — what is it?	The angle locating a rotating object relative to a reference direction. Degrees must be converted to radians before rotational relationships are used.
Angular acceleration — what is it?	The rate at which angular velocity changes. It is zero for uniform circular motion even though the linear acceleration is not.
Centripetal acceleration — what is it?	The acceleration directed toward the centre of a circular path. It exists even at constant speed, because the direction of velocity keeps changing.
Vertical circular motion — what is it?	Circular motion in a vertical plane, as on a loop. The minimum speed at the top is where the normal force reaches zero, not where the speed is zero.
Torque — what is it?	The turning effect of a force about an axis. A force through the axis produces no torque however large it is.
Sign of torque — what is it?	Whether a torque tends to turn an object one way or the other. The sign convention must be fixed before torques are summed.
Rotational inertia — what is it?	The resistance of an object to angular acceleration. It is not a fixed property of an object. It changes when the axis changes.
Comparing common shapes — what is it?	How rotational inertia differs among simple bodies of equal mass and radius. Mass concentrated near the rim always gives a larger value.
Rotational form of the second law — what is it?	The relationship between net torque and angular acceleration. The rotational inertia takes the role of mass, and it is not the same as mass.
Rolling without slipping — what is it?	Motion in which the contact point does not slide. Static friction acts at the contact point and does no work in this case.
Angular momentum — what is it?	The rotational analogue of linear momentum. It depends on the axis chosen, so the axis must be stated.
Conservation of angular momentum — what is it?	The principle that angular momentum is constant when no net external torque acts. It is a separate law from conservation of linear momentum, and one can hold while the other fails.
Angular impulse — what is it?	The product of torque and the time over which it acts. It is the rotational counterpart of impulse and follows the same reasoning.
Static equilibrium conditions — what is it?	The two requirements for an object to remain at rest. Satisfying only one condition is not enough.
Newton's law of universal gravitation — what is it?	The statement that every mass attracts every other mass. The distance is measured between centres, not between surfaces.
Gravitational field strength — what is it?	The gravitational force per unit mass at a point. It is a property of the field, so it does not depend on the test mass.
Orbital motion — what is it?	The motion of a satellite held in a circular path by gravity. A satellite in orbit is in free fall, not weightless because gravity has vanished.
Orbital period — what is it?	The time a satellite takes to complete one orbit. Doubling the radius more than doubles the period.
Apparent weightlessness — what is it?	The sensation experienced by an orbiting astronaut. Gravity is still acting, and it is what keeps them in orbit.
Gravitational potential energy at large distances — what is it?	The stored energy of two masses separated by a large distance. The simple product of weight and height applies only near a surface.
Simple harmonic motion — what is it?	Oscillation in which the restoring force is proportional to the displacement and opposite to it. Not every oscillation is simple harmonic. The proportionality must hold.
Amplitude — what is it?	The greatest displacement from equilibrium during an oscillation. It does not affect the period of an ideal mass-spring system or a small-angle pendulum.
Frequency — what is it?	The number of complete cycles per second. Angular frequency is two pi times this value, and the two must not be interchanged.
Energy in simple harmonic motion — what is it?	The exchange between kinetic and potential energy during oscillation. Kinetic energy is greatest at equilibrium, not at the extremes.
Simple pendulum — what is it?	A mass swinging on a light string. The period does not depend on the mass of the bob.
Pendulum on another planet — what is it?	How the period changes with gravitational field strength. Changing the mass of the bob has no effect.
Mechanical wave — what is it?	A disturbance that travels through a medium carrying energy. The medium itself is not transported along with the wave.
Wavelength — what is it?	The distance between successive identical points on a wave. It is a distance in space, not a time.
Superposition — what is it?	The principle that overlapping waves add displacement by displacement. The waves pass through each other unchanged after overlapping.
Standing wave — what is it?	A pattern formed when two identical waves travel in opposite directions. It is not a wave moving very slowly. Nothing propagates.
Fundamental frequency — what is it?	The lowest frequency at which a standing wave forms. Higher harmonics are whole-number multiples of it only for a string or an open pipe.
Sound as a wave — what is it?	A longitudinal pressure wave travelling through a medium. Sound cannot travel through a vacuum.
Electric charge — what is it?	A property of matter that produces electrical forces. Charge is conserved. It is transferred, never created.
Resistance — what is it?	The opposition a component offers to current. It is a property of the component, not of the circuit it sits in.
Adding resistors in parallel — what is it?	Finding the combined resistance of parallel branches. Forgetting the final reciprocal is a common and large error.
Electrical power — what is it?	The rate at which electrical energy is transferred. The forms using resistance follow from Ohm's law and apply only to ohmic components.
Ammeter and voltmeter — what is it?	Instruments for measuring current and potential difference. 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 does not use your AI allowance, 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.