AP Physics 1 Vocab + Formulas

how to measure velocity?

motion sensor OR ruler and timer

how to measure period?

stopwatch — take multiple cycles to reduce error (total time/# of cycles)

how to measure acceleration?

motion sensor OR calculate w/ kinematic equations

how to calculate rotational velocity

rotational motion sensor OR ruler and timer

how to measure volume?

graduated cylinder (drop sinking object in and see the change in water)

constant speed equation

s = d/t

distance over a constant speed equation

d = st

average v equation that can be used any time AND average v equation that can be used only at constant acceleration

acceleration equation

a = v/t

kinematic equations

• v_f = v₀ + at

• x = x₀ + v₀t + ½at²

• v² = v₀² + 2aΔx

when can the kinematics equations be used?

at constant acceleration

slope of what graph gives us velocity?

position v. time

how do we determine instantaneous position on a graph

look at a single point

slope of what graph gives us acceleration?

velocity vs. time

area of what graph gives us displacement?

velocity vs. time

free fall

only has acceleration and velocity in the y-direction downward + only force acting on it is gravitational force

how can we solve for t in projectile motion?

using the y component

acceleration of the y component in projectile motion

-g or -9.8m/s²

uniform vs. nonuniform motion

uniform = zero acceleration

nonuniform = nonzero acceleration

reference frame equation

U_AB = V_Ag - V_Bg

Newton’s First Law

an object maintains its velocity unless acted on by a nonzero net force

Second Law

F_net = ma

Third law

every action has an opposite and equal reaction

action reaction pairs

ALWAYS 2 objects with 2 forces (objects acting on each other)

because of the third law, motion of two objects WITHIN a system does not affect ___

because of ___, motion of two objects within a system does not affect the total motion of the system

Friction force formula (static and kinetic)

• F_k = μ_kF_N

• F_S ≤ μ_SF_N

Is Fs or Fk typically larger?

Fs is typically larger than Fk

What does it mean if the rope has mass?

higher tension force at a higher point on the rope b/c it has to support its own weight

Normal force

made from two surfaces pushing against each other

spring force equation

-F = -kx

where k = spring constant

and x = the distortion of spring from natural length

center of mass equation in terms of POSITION

COM = COM = Σm_ix_i/Σm_i

center of mass equation in terms of VELOCITY

v_COM = Σm_iv_i/Σm_i

what units is center of mass in?

cm

how do we solve inclined plane problems?

rotate x-axis to the surface + resolve forces for Fg (angle of incline = angle between mg and mgy)

atwood machine pulleys — how to solve them?

use the direction of acceleration to simplify the FBD into one dimension

apparent weight

normal force

what is the apparent weight in free fall?

0

do we feel heavier or lighter when acceleration upward?

feel heavier b/c the net force increases

Direction of velocity and acceleration for an object in uniform circular motion

velocity direction is always tangent to the circle

acceleration direction is always pointing towards center

directions of acceleration and velocity are perpendicular

velocity formula for object in UCM

s = 2πr/T = 2πrf

acceleration formula for object in UCM

a = v²/r

T/F: we put centripetal force in the FBD

FALSE. another force must cause centripetal force —> centripetal force = net force

centripetal force formula

F_C = mv²/r

UCM

motion of an object moving in a circle with a constant radius and a constant speed

is velocity constant in UCM?

no b/c direction changes

examples of forces keeping an object in UCM

tension force, static friction force

What is important to note about acceleration when solving for objects in UCM?

the DIRECTION (change the sign accordingly)

what does static friction do to an object in horizontal UCM?

prevents radial motion —> causes Cf

How do solve tension force in a Conical Pendulum?

Resolve forces!

where is g strongest?

gravitational force is strongest at the planet’s surface

does g get larger as you get closer to the planet’s core?

NO—it gets smaller b/c the mass pulling the object in decreases I think

grav field equation

g = MG/r² 

how do we measure radii between large bodies for grav field questions?

from CENTER to CENTER

distance equation when an object is a height above the planet

r = R + h

Force due to gravity equation

Gm₁m₂/r²

Where to find the gravitational constant?

on formula sheet

how do we determine relationship if one variable changes?

derive equation for the dependent variable

Newton’s Law of Universal Gravitation

all objects attract each other with a Fg —> gravity is attractive

formula to calculate period and velocity of object in orbit (hint: it starts with the velocity equation and net force equation in UCM)

what is your apparent weight if you are in orbital motion?

ZERO — you’re constantly in free fall and Fg is the only force acting on you —> accelerating towards the planet but not GOING towards the planet

why are you not going toward the planet in orbital motion if your acceleration is directed at it?

b/c you have a velocity tangent to the orbital path

What is true about energy in an open system?

not conserved

Work

change in energy of a system

what does work and to what does it do work to?

environment does work on system

What type of forces is work dependent on?

ONLY depends on forces that are parallel to displacement

When does work = 0? (3)

• constant force

• object doesn’t move

• object moves perpendicular to force

when is Work positive?

force and displacement same direction

when is Work negative?

force and displacement opposite direction

Work equation

W = F_APPd

KE equation

½mv²

GPE equations (2)

• GPE = mgΔh ← for objects on surface

• GPE = -GMm/r ← for objects far from surface

EPE equation

½kx²

Mechanical energy — what does it take into account and equation

everything BESIDES internal energy…

For closed system: ME = KE + GPE + EPE

Properties of conservative forces (these have to do with paths)

• Work is PATH INDEPENDENT — it only depends on final and initial position

• In a closed path, W = 0

Power

rate of change of energy

Power equations (4 but 2 main ones)

• P = ΔE/Δt

  • P = W/Δt

  • P = FΔx/t

• P = F*v_parallel

escape velocity — what is it and what is the formula?

minimum velocity for an object to escape a grav field

• v_escape = √2GM/r

momentum — what is it and equation

how hard it is to stop a MOVING object (depends on MASS and VELOCITY)

p = mv

how do we know if something is vector or scalar?

look at the equation — if it does not depend on vector quantities or if those vector quantities are squared, it is scalar

Impulse — what is it and equations (3)

the change in momentum

• I = FΔt = Δp = mΔv

• measured in Ns

how do we change momentum?

OUTSIDE force (causes an impulse)

inelastic collisions (perfect and general)

two objects collide + KE changes to something else

• perfect: stick together

• general: bounce off, but transfer some KE into other forms

elastic collisions

two objects collide + bounce off and KE is conserved

explosions

object breaks into multiple pieces + potential energy is converted to KE

What is the linear displacement if a point moves an entire circumference?

2πr

angular velocity equation for an object in UCM using freqency

⍵ = 2πf

how do we convert linear quantities to rotational quantities?

divide by radius r

what would make the rotational motion equations false?

if the object slips or slides

Why is torque different from work and energy?

torque has a DIRECTION

Is work scalar or vector?

scalar

torque equation

Work done by torque equation

W = τΔΘ

When does torque = 0?

when the force is applied at the Axis of Rotation

what is moment of inertia dependent on and inertia equation?

how far the average mass is from the axis of rotation —> the farther the dist of mass from AoR, the harder it is to start rotating and to stop rotating

I = Σm_ir²

does a hoop or a sphere have more rotational inertia?

hoop

is it harder to stop a hoop or a sphere from rotating?

hoop — more inertia

what is moment of inertia a measure of?

object’s resistance to ANGULAR acceleration due to an applied torque

what causes rotation on an inclined plane?

friction force provides the torque

Parallel Axis Theorem

I = I_cm + MD²

where D = distance from Center of Mass