ALL AP PHYSICS ACTIVE RECALL

What makes a quantity a scalar vs a vector?

A scalar has magnitude only, while a vector has both magnitude and direction.

What is displacement?

Displacement is the change in position from initial to final location, including direction.

What is the difference between distance and displacement?

Distance is total path length traveled, while displacement only cares about final position minus initial position.

What does average velocity tell you?

It tells you displacement per time interval, not total distance per time interval.

What does average acceleration tell you?

It tells you how much velocity changes per time interval.

When is an object accelerating?

An object accelerates whenever its velocity changes in magnitude, direction, or both.

Does zero acceleration mean zero velocity?

No, zero acceleration just means velocity is not changing.

What does the slope of a position-time graph represent?

The slope of an x-t graph represents velocity.

What does the slope of a velocity-time graph represent?

The slope of a v-t graph represents acceleration.

What does the area under a velocity-time graph represent?

The area under a v-t graph represents displacement. This was one of your recurring review points.

What does the area under an acceleration-time graph represent?

The area under an a-t graph represents change in velocity. This also showed up in your notes.

What is instantaneous velocity?

Instantaneous velocity is the slope of the tangent line to the position-time graph at one moment.

What is instantaneous acceleration?

Instantaneous acceleration is the slope of the tangent line to the velocity-time graph at one moment.

When can the constant-acceleration kinematic equations be used?

They can only be used when acceleration is constant in the chosen direction.

How is vertical motion near Earth usually modeled?

As motion with constant downward acceleration due to gravity.

What is a reference frame?

A reference frame is the viewpoint from which motion is measured.

How do you handle relative velocity in one dimension?

Treat velocity as signed and add or subtract using direction, not vibes.

What stays independent in projectile motion?

Horizontal and vertical motion are analyzed separately.

What is true about horizontal acceleration in ideal projectile motion?

It is zero if air resistance is negligible.

What controls the time a projectile stays in the air?

Its vertical motion does.

What controls how far a projectile travels horizontally?

Its horizontal speed together with its time in the air.

If two projectiles have the same initial vertical velocity, what do they share?

They have the same vertical motion and same time to reach the same vertical position, if launched from the same height.

What is a system in physics?

A system is the object or group of objects you choose to analyze.

When can a system be treated like a single object?

A system can be treated like a single object when the internal details are not important to the motion being analyzed.

What is apparent weight?

Apparent weight is the normal force exerted on an object, which is not always equal to the gravitational force.

When does an object appear weightless?

An object appears weightless when gravity is the only force acting on it, or when no forces act on it.

Where is the center of mass for a symmetric object?

It lies on the object’s lines of symmetry.

What does the center of mass let you do?

It lets you model a system’s motion as if all the mass were concentrated at one point.

What does a free-body diagram show?

It shows all external forces exerted on one chosen object or system.

What should never appear on a free-body diagram?

Forces the object exerts on other things, or force components unless you choose to resolve them separately.

What is a force?

A force is an interaction between two objects or systems.

What causes contact forces at the microscopic level?

They come from electric interactions between atoms and molecules.

What are common contact forces?

Normal force, friction, tension, and spring force.

What does Newton’s third law say?

If object A exerts a force on object B, then B exerts an equal-magnitude, opposite-direction force on A.

What assumptions define an ideal string?

Negligible mass and no stretch, so tension is the same throughout.

In a hanging rope with mass, where is tension greatest?

At the top, because it supports more of the rope below. That exact idea was in your notes.

What is translational equilibrium?

It means the net force on the object or system is zero.

If net force is zero, what can the velocity be?

Zero or any constant velocity.

What does Newton’s first law really say?

With zero net force, velocity stays constant.

If net force doubles and mass stays the same, what happens to acceleration?

Acceleration doubles.

If mass doubles and net force stays the same, what happens to acceleration?

Acceleration is cut in half.

What is weight?

Weight is the gravitational force exerted on an object.

When do apparent weight and true weight differ?

When the object is accelerating vertically.

In Newton’s law of gravitation, what does r mean?

It is the distance between the centers of mass of the two objects.

What direction is gravitational force?

Along the line between the centers of mass, always attractive.

What is static friction?

Static friction acts when surfaces do not slide relative to each other.

What is kinetic friction?

Kinetic friction acts when surfaces slide relative to each other.

Which can be larger, static or kinetic friction?

Maximum static friction is usually larger than kinetic friction

Does static friction always equal its maximum value?

No, it adjusts up to a maximum as needed.

What does friction mainly depend on in this course?

The nature of the surfaces and the normal force.

What does the spring constant k tell you?

A larger k means a stiffer spring that resists stretch/compression more.

In Hooke’s law, what does x mean?

It is displacement from equilibrium or unstretched length, depending on setup

What direction does the spring force point?

Opposite the spring’s displacement from equilibrium.

What is centripetal acceleration?

It is the inward acceleration of an object moving in a circle.

What direction is centripetal acceleration?

Always toward the center of the circular path.

Is centripetal force a new separate force?

No, it is the name for the net inward force causing circular motion.

What is the period in circular motion?

The period is the time for one full revolution.

What is a common circular-motion mistake?

Forgetting that even if speed is constant, the object is still accelerating because direction changes.

What is an ideal pulley?

A pulley with negligible mass that rotates with negligible friction.

Do internal forces change a system’s center-of-mass motion?

No, internal forces do not affect the motion of the system’s center of mass.

Does friction depend on contact area in AP Physics 1?

No, not in the model used here.

What is inertial mass?

A measure of how much an object resists changes in motion.

What does AP Physics 1 say about inertial and gravitational mass?

They are experimentally equivalent.

What is kinetic energy?

Kinetic energy is the energy an object has because of motion.

Is kinetic energy a scalar or vector?

It is a scalar.

Can two observers measure different kinetic energies for the same object?

Yes, because kinetic energy depends on speed, and speed depends on reference frame.

What is work?

Work is energy transferred into or out of a system by a force acting over a displacement. Your notes simplified this as energy transferred in or out of a system.

What part of a force does work?

Only the component parallel to the displacement.

What kind of energy can a single-object system have?

A single-object system can have kinetic energy, but it cannot have potential energy by itself.

Why does potential energy belong to a system instead of one object?

Potential energy depends on the positions of objects interacting through conservative forces, so it belongs to the system.

What is the difference between conservative-force work and nonconservative-force work?

Conservative-force work is path independent, while nonconservative-force work depends on the path taken.

What does the area under a force-versus-displacement graph represent?

The area under a force-versus-displacement graph represents work.

What does a perpendicular force component do?

It can change direction without changing kinetic energy.

When is work positive?

When the force component points in the same direction as displacement.

When is work negative?

When the force component points opposite the displacement.

When is work zero?

When there is no displacement, or the force is perpendicular to the displacement.

What does the area under a force-position graph represent?

Work.

What does the work-energy theorem say?

Net work on an object equals the change in its kinetic energy.

What is a conservative force?

A conservative force does path-independent work and can be associated with potential energy.

What are common conservative forces in AP Physics 1?

Gravity and ideal spring force.

What is a nonconservative force?

A nonconservative force does path-dependent work and usually dissipates mechanical energy.

What are common nonconservative forces in AP Physics 1?

Friction and air resistance.

Can you choose zero potential energy anywhere?

Yes, as long as you stay consistent.

What determines elastic potential energy?

The spring constant and how far the spring is stretched or compressed from equilibrium.

What determines gravitational potential energy near Earth’s surface?

Mass, gravitational field strength, and vertical position change.

What is the most important conservation-of-energy idea?

Track energy in the whole system and include transfers into or out of the system.

When is mechanical energy conserved?

When only conservative internal forces do work on the system.

What happens to mechanical energy when friction acts?

Some mechanical energy is transformed into thermal energy or sound, not destroyed.

Does gravity automatically mean energy is “lost”?

No, gravity is conservative

What is power?

Power is the rate of energy transfer or the rate of doing work

Why can a ramp feel easier than stairs?

It requires less force at a time, even though total work against gravity can be the same if height is the same.

What is momentum?

Momentum is mass times velocity and measures how hard it is to stop or redirect motion.

Is momentum a scalar or vector?

It is a vector and points in the same direction as velocity.

Why is momentum useful?

It is especially helpful for collisions, explosions, and short interactions.

What is a collision in AP Physics 1?

A collision is an interaction where internal forces during the interaction are much larger than external forces.

What is an explosion in AP Physics 1?

An explosion is an interaction where internal forces push parts of the system apart.

What happens to momentum when there is no net external force on a system?

The total momentum of the system remains constant.

What happens to momentum when there is a net external force on a system?

Momentum is transferred between the system and its surroundings.

What is a perfectly inelastic collision?

A perfectly inelastic collision is one in which the objects stick together and move with the same final velocity.

What is impulse?

Impulse is the effect of a force acting over a time interval.