ap physics 1
👉 AP Physics Essentials
👟 Unit 1  Kinematics
🌀 Unit 2  Dynamics
🚀 Unit 3  Circular Motion
⚡️ Unit 4  Energy
⛳️ Unit 5  Momentum
🎸 Unit 6  Simple Harmonic Motion
🎡 Unit 7  Torque & Rotational Motion
💡 Unit 8  Electric Charges & Electric Force
🔋 Unit 9  DC Circuits
🔊 Unit 10  Mechanical Waves & Sound
10.3Interference and Superposition (Waves in Tubes and on Strings)
✍️ Free Response Questions (FRQs)
🧐 Multiple Choice Questions (MCQs)
#velocity
#acceleration
⏱️ 5 min read
written by
peter apps
(editor)
October 24, 2020
All forces share certain common characteristics when considered by observers in inertial reference frames. (A frame of reference in which a body remains at rest or moves with constant linear velocity unless acted upon by forces)
Key Vocabulary: Frame of Reference  a point of view 👀
⟶ Motion involves the change in position of an object over a period of time, and it is measured in reference to another object.
EXAMPLE: Two students are in a classroom sitting at their desks. Are they moving relative to each other?
Are they moving relative to the solar system?

Essential Knowledge 3.A.1 🏘
An observer in a reference frame can describe the motion of an object using such quantities as position, displacement, distance, velocity, speed, and acceleration.
Key Vocabulary: Position  a location relative to a fixed point
⟶ You can represent position in a Position (m) vs. Time (s) Graph (pictured below)
Image courtesy of ck12.org
Interpreting the Graph
To determine which way an object is moving look at which way the Position vs. Time Graph is sloped
A front slash / indicates that an object is moving away from the detector
A black slash \ indicates that an object is moving towards the detector
The slope of a Position vs. Time Graph is equal to velocity
When the slope is a straight line it has constant velocity
When the slope is a curved lived there is acceleration (a change in velocity)
When the slope is zero the object is at rest
The yintercept is the initial displacement of an object
⟶ Still feeling a little confused on Position vs. Time Graphs? Don’t worry! Check out this video from Khan Academy for more practice!
Key Vocabulary: Scalar  quantities that are described by magnitude (a numerical value) alone
Example: She is five feet tall
Distance and Speed are scalar quantities
Key Vocabulary: Vector  quantities that are described by a size (magnitude) and a direction (ex. East, Up, Right, etc.)
Example: The gas station is five miles west from the car
Displacement, Velocity, and Acceleration are vector quantities
Vectors can also be represented by arrows, and the length of the arrow should represent the magnitude of the described quantity. From the image below you can see the 5m arrow is smaller in length than the 50m arrow to reflect the difference in magnitude of the two quantities.
⟶ Are you still feeling a little confused about Scalar vs. Vector Quantities? Don’t worry! Check out this video from Khan Academy for more practice!
Key Vocabulary: Displacement  how far an object is from its original position
Vector quantity
Express with a Sign (+ or ) or Direction (North, Down, Left, etc.)
SI Unit: Meter (m)
We use the symbol Δx to indicate displacement
⟶ Typical Displacement Question: How far are you from home?
Key Vocabulary: Distance  how far an object has traveled
Scalar quantity
Needs no frame of reference
SI Unit: Meter (m)
⟶ Typical Distance Question: How far did you travel?
As you can see from the image below, distance takes into account the journey an object takes whereas displacement is concerned with the frame of reference of the original position.
Image Couretsy of thescienceclassroom.org
EXAMPLE: A car travels 25 meters around a circular track and ends at its original position. What is its distance?
What is its displacement?

⟶ Still feeling a little confused about Distance vs. Displacement? Don’t worry! Check out this video from Khan Academy for more practice!
Key Vocabulary: Speed  describes how fast a particle is moving
Scalar quantity
SI Unit: Meters (m)/Seconds (s)
Equation: S = D/t
Key Vocabulary: Velocity  speed in a given direction
Vector quantity
SI Unit: Meters (m)/Seconds (s)
Equation: V = x/t
⟶ You can represent velocity in a Velocity (m/s) vs. Time (s) Graph (pictured below)
Image Courtesy of ck12.org
Interpreting the Graph
To determine which way the object is moving look at whether the Velocity vs. Time Graph is above or below the horizontal axis (xaxis)
An object is moving away from the detector if it’s above
An object is moving towards the detector if it’s below
The yintercept is the initial velocity of an object
The slope of a velocity graph is equal to the acceleration
When the slope is zero the object has constant velocity
When the slope is a straight line it has constant acceleration
When the slope is a curved line there is changing acceleration
The area under the curve is displacement
The object is stopped when y = 0
⟶ The table below is a type of motion cheat sheet. Memorizing this will help you ace any quizzes or tests with graph interpretation present!
Velocity  Acceleration  Type of Motion 
V = 0  A = 0  At rest 
V = (+) or ()  A = 0  Constant velocity 
V = (+)  A = (+)  Speeding up 
V = ()  A = ()  Speeding up 
V = (+)  A = ()  Slowing down 
V = ()  A = (+)  Slowing down 
FRQ PRACTICE: Want more practice with Velocity and Average Velocity? Check out these FRQs from the 2016 AP Physics 1 exam. 
Key Vocabulary: Acceleration  a change in velocity (magnitude or direction)
Equation: Aavg = V/t
⟶ You can represent acceleration in an Acceleration (m/s/s) vs. Time (s) Graph (pictured below)
Image courtesy of khanacademy.org
Interpreting the Graph
The yintercept is the initial acceleration of an object
When the slope is zero the object has constant acceleration
The area under the curve is velocity
EXAMPLE: (Reference the Graph above to answer the following questions) What is the velocity of the object from 0s  7s?
What is the velocity of the object from 7s  9s?

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