Motion

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 MotionUniform 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 • 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 motionNon 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/s2) = 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 vsScalar quantities • Uniform motion vs Non uniform motion • Math • Speed • Velocity • Acceleration • Graphs • Speed-Time • Distance-Time • Velocity-Time • Position-Time