MOTION

MOTION

1. Describing Motion?

   • Motion: An object is in motion if its distance from another object is changing
   • Reference Point(s): A place or object used for comparison to determine if something is in motion
     • An object is in motion if it changes position relative to a reference point
     • Stationary Objects (Tree, sign, building), make good reference points
       • If a passenger is moving relative to a tree, it's concluded that the train is in motion
   • Relative Motion
     • "Calculation of the motion of an object with regard to some other moving object."
   • Measuring Distance
     • We use units of measurement to describe motion precisely
     • International System of Units, In French: System International (SI)
       • Scientists all over the world need to use the same unit of measurement in order to communicate clearly
         • Meter: A unit of measurement
         • Use SI units to describe quantities other than length

2. Speed?

   • Calculating Speed
     • A measurement of distance can tell you how far an object travels
     • If you know the distance an object travels in a certain amount of time, you can calculate the speed of the object.
   • Speed: A type of rate
     • Rate tells the amount of something that occurs or changes in one unit of time
     • Speed of an object is the distance the object travels per unit of time
   • Speed Equation
     • Speed = Distance/Time
       • To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance
   • Average Speed
     • To calculate average speed, divide the total distance traveled by the total time
   • Instantaneous Speed
     • The rate at which an object is moving at a given instant in time

3. Velocity?

   • Knowing the speed at which something travels doesn't tell everything about motion
     • To describe an objects motion completely, you need to know the direction of motion
   • Velocity: Speed in a given direction
     • When you know both the speed and direction of an object's motion, you know the velocity of the object

4. Graphing Motion?

   • You can show the motion of an object on a line graph in which you plot distance versus time
   • Slope: Steepness of a line on a graph
     • Slope tells how fast a variable changes in relation to another variable
     • The steeper the slope, the greater the speed.
     • Constant slope represents motion at a constant speed
     • Slope = Rise/Run
   • Calculating Slope
     • You can calculate slope of a line by dividing the rise by run
     • Slope = Rise/Run
   • Different Slopes
     • Most moving objects don't travel at a constant speed

5. Acceleration?

   • Acceleration: The rate at which velocity changes
     • In science, acceleration refers to increasing speed, or changing direction
   • Increasing Speed: When an object's speed increases, the object accelerates
   • Decreasing Speed: When an object's speed decreases, the object slows down
   • Changing Direction: An object that is accelerating, but changing speed
   • To determine acceleration of an object moving in a straight line, you must calculate the change in speed per unit of time
   • Acceleration = Final Speed - Initial Speed/Time
   • You can use both a speed-versus-time graph and a distance-versus-time graph to analyze the motion of an accelerating object.

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