Motion

Motion

1. Describing Motion with Words

   • Mechanics
     • The study of the motion of objects
     • Kinematics
       • the science of describing the motion of objects using
         • Words
         • diagrams
         • numbers
         • graphs
         • equations
   • Scalar
     • quantities that are fully described by just a magnitude (numerical value)
   • Vectors
     • quantities that are fully described by both a magnitude and a direction.
   • Distance
     • a scalar quantity that refers to "how much ground an object has covered" during its motion.
   • Displacement
     • a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.
   • Speed
     • a scalar quantity that refers to "how fast an object is moving."
       • the rate at which an object covers distance
     • Average Speed
       • the average of all instantaneous speeds; found simply by a distance/time ratio.
     • Instantaneous
       • the speed at any given instant in time.
   • Velocity
     • a vector quantity that refers to "the rate at which an object changes its position."
       • the rate at which the position changes
     • vector quantity
       • direction aware
         • The direction of the velocity vector is simply the same as the direction that an object is moving
   • Acceleration
     • a vector quantity that is defined as the rate at which an object changes its velocity
       • acceleration has nothing to do with going fast
         • It has to do with changing how fast an object is moving. If an object is not changing its velocity, then the object is not accelerating.
     • Constant Acceleration
       • an accelerating object that will change its velocity by the same amount each second
     • The direction of the acceleration vector depends on two things
       • whether the object is speeding up or slowing down
         • If an object is slowing down, then its acceleration is in the opposite direction of its motion.
           • Positive acceleration
             • When an object is speeding up, the acceleration is in the same direction as the velocity
             • when an object is slowing down, the acceleration is in the opposite direction as the velocity
           • Negative acceleration
             • when an object is slowing down, the acceleration is in the opposite direction as the velocity
             • When an object is speeding up, the acceleration is in the same direction as the velocity
       • whether the object is moving in the + or - direction

2. Describing Motion with Diagrams

   • Ticker tape diagrams
     • Ticker tape analysis
       • a common way of analyzing the motion of objects
         • A long tape was attached to a moving object and threaded through a device that placed a tick upon the tape at regular intervals of time
           • As the object moved, it dragged the tape through the "ticker," which left a trail of dots.
             • The trail of dots gave a history of the object's motion so a representation of the object's motion.
         • The distance between dots on a dot diagram represents the object's position change during that time interval
           • A large distance between dots indicates that the object was moving fast during that time interval
           • A small distance between dots means the object was moving slow during that time interval
           • A changing distance between dots indicates a changing velocity (acceleration)
           • A constant distance between dots represents a constant velocity (no acceleration)
   • Vector diagrams
     • diagrams that depict the direction and relative magnitude of a vector quantity by a vector arrow
       • can be used to describe the velocity of a moving object during its motion
         • the magnitude of a vector quantity is represented by the size of the vector arrow
           • If the size of the arrow in each consecutive frame of the vector diagram is the same, then the magnitude of that vector is constant
     • vector diagrams will be used to represent a variety of physical quantities such as
       • acceleration
       • force
       • momentum

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