1. Motion Energy Flow in Technological Systems Unit C

2. Motion  Motion of an object occurs when an imaginary line joining object to reference point changes in length, direction or both  Analyze motion of object only if we compare objects position to another point (reference point)  Once we know motion is present we can describe type & rate of motion

3. Simplest form of Motion Uniform Motion  Object that travels at constant rate of motion in straight line moving in uniform motion  Use term Average speed to describe it  Average speed is uniform motion that involves traveling a distance in a specified time

4. Average Speed  Formula to determine an objects average speed Average speed = distance traveled time elapsed v (m/s) = d (m) = d final – d initial t (s) t final – t initial means change in

5. Example  You can now use this formula to determine the average speed of object A person walks 10.0m away from a stop sign in 5.00s. What is the average speed of the person?

6. Analyze average speed/uniform motion  Graphs provide visual representation of motion and shows relationship between two variables  2 types of graphs to describe Uniform motion 1. Distance-Time Graphs What does it look like?  Plot distance vs time  Distance in meters on the y axis and Time in seconds on the x axis  Line will be straight with a positive slope What does it tell us?  Shows us direct relationship between distance traveled and time it takes  Straight line means uniform motion  Slope of the line tells you the average speed of the object  The steeper the slope the faster the speed

7. 2. Speed-Time Graphs What does it look like?  Plot speed vs time  Speed in m/s on the y axis and Time in seconds on the x axis  Line will be level and straight What does it tell us?  Shows us whether the object was moving in uniform motion  If slope of the line is zero it tells you the average speed of the object was constant  Area under the line also helps us calculate the distance the object traveled

8. Vectors and Scalar Quantities  Scalars are quantities that describe the size or amount (magnitude) e.g. speed, distance, time  Vectors are quantities that describe direction as well as magnitude e.g. velocity, displacement, position  An arrow is placed above the number or symbol to indicate it as a vector

9. Distance vs. Displacement  Distance is scalar describing the length between 2 points or locations (d)  Displacement/Position is vector describing distance between 2 points AND the change in direction that took place (d [E])  When writing displacement always include direction object was moving in square brackets

10. Velocity vs. Speed  Speed is scalar describing the distance an object travels during a given time (v) Remember v (m/s) = d (m) = d final – d initial t (s) t final – t initial  Velocity is vector describing the displacement of an object during a given time ( v [E] ) ( v [E](m/s) = d [E] (m) = d [E]final – d[E] initial t (s) t final – t initial

11. Analyze Velocity  Graphs provide visual representation of motion and shows relationship between two variables 1. Position -Time Graph  Plots position (displacement) on the y axis and time on the x axis  Shows us in position of an object in relation to the passing time  If line is straight we assume object is moving in uniform motion  Slope of the line is equal to the objects velocity

12. Most common form of motion Non Uniform motion  Occurs when there is a change in the speed of an object over the period of time  Object is moving at a inconsistent rate  Speeding up/accelerating  Slowing down/decelerating  Use the term acceleration to describe it  Acceleration is non uniform motion that involves speeding up or slowing down in a specified time

13. Acceleration  Formula to determine an objects acceleration/deceleration Acceleration= change in speed time elapsed a (m/s 2 ) = v (m/s) = v final – v initial t (s) t final – t initial means change in if the answer is positive means speeding up if answer is negative means slowing down

14. Example A train starts from rest and reaches a velocity of 54 km/h in 10.0s. What is the acceleration? A golf ball rolling on a green slows down from 2.00 m/s to 1.50 m/s in 2.00 s. What is the rate of deceleration?

15. Analyze acceleration/non uniform motion  Graphs provide visual representation of motion and shows relationship between two variables  2 types of graphs to describe non uniform motion 1. Position-Time Graphs What does it look like?  Plot position vs time  Position in meters (include direction) on the y axis and Time in seconds on the x axis  Line will be smooth and curved What does it tell us?  Shows us the direct relationship between position of object and time taken to travel  Shape of the curve of the line tells us whether the object was accelerating or decelerating  If slope gradually increasing the object is accelerating  If slope gradually decreasing the object is decelerating

16. 2. Velocity-Time Graphs What does it look like?  Plot velocity vs. time to determine whether the object is accelerating or decelerating  Velocity (m/s) with direction on the y axis and time (seconds) on the x axis  The line of best fit is straight with either an increasing slope or a decreasing slope What does it tell us?  The slope of the line tells us whether the object was accelerating or decelerating  If slope is increasing then the object was accelerating  If the slope is decreasing then the object was decelerating  A straight horizontal line shows the object was uniform motion

17. Motion Quiz  Units, sig digs, scientific notation  Vector vs Scalar quantities  Uniform motion vs Non uniform motion  Math  Speed  Velocity  Acceleration  Graphs  Speed-Time  Distance-Time  Velocity-Time  Position-Time