1. Electricity and Magnetism
PHYSICS
Units:
Analyzing Motion
Work and Energy
Waves
Electricity and Magnetism

2. TN Standards - Motion
CLE : Investigate the relationships among speed, position, time, velocity, and acceleration
CLE.3202.Inq.2: Design and conduct scientific investigations to explore new phenomena, verify, previous results, test how well a theory predicts, and compare opposing theories
CLE.3202.Inq.4: Apply qualitative and quantitative measures to analyze data and draw conclusions that are free of bias
CLE.3202.Inq.6: Communicate and defend scientific findings

3. Chapter 11 - Motion Sections: 1 - Measuring Motion 2 - Acceleration
3 - Motion and Force

4. 1 - Measuring Motion Key Questions:
How is a frame of reference used to describe motion?
What is the difference between speed and velocity?
What do you need to know to find the speed of an object?
How can you study speed by using graphs?

5. Frame of Reference
Observe an object in relation to other objects that stay in place, called reference points.
A frame of reference is used to describe the motion of an object relative to these reference points.
The trees in the background
in Figure 1

6. Distance Distance measures the path taken
To measure distance, you measure the length of the path that the object took.
Displacement measures only the difference between the final and starting positions

7. Speed & Velocity Speed – how fast an object moved
Velocity – gives us both speed and direction
Velocity is described relative to a reference point
Up and right are positive; left and down are negative ( Cartesian Coordinate system ) +y -x +x -y

8. Motion
When an object changes position with respect to a frame of reference, the object is in motion
Velocity / Speed: Distance travelled in a certain time period D
V/S t

9. D V/S t Calculating Speed
Need two quantities – distance travelled & time
Average speed – distance divided by time interval
Instantaneous speed
speed at a given time
very small time interval
Speedometer in car D
V/S t

10. Demonstration Slope of a distance vs. time graph equals speed
Run a 6 m length ( in class? )
Have your partner time you
What is your speed?

11. Graphing Motion
Sometimes easier to analyze motion on graphs

12. 2 - Acceleration Key Questions:
What changes when an object accelerates?
How do you calculate the acceleration of an object moving in a straight line?
How can a graph be used to find acceleration?

13. Velocity Changes upon Acceleration
Speed can change, but so can direction
Notice speed is changing with each second

14. Changes in Direction
Uniform circular motion has centripetal acceleration
Sources: friction, tension
Demonstration

15. Circular Motion Demonstration
Foam ball with string attached to it
Swing ball with hand
Diagram features of motion
What happens when I let go of the string?

16. 2 - Acceleration Key Questions:
What changes when an object accelerates?
How do you calculate the acceleration of an object moving in a straight line?
How can a graph be used to find acceleration?

17. BELLWORK
What changes when acceleration occurs?

18. 2 - Acceleration Key Questions:
What changes when an object accelerates?
How do you calculate the acceleration of an object moving in a straight line?
How can a graph be used to find acceleration?

19. Calculating AccelerationV A t

20. Calculating Acceleration
Acceleration is the rate at which velocity changes
Acceleration is negative when slowing down

21. Graphing Accelerated Motion
The slope of a straight line on a speed vs. time graph is equal to the acceleration.
Constant Acceleration
Can also be seen from a distance vs. time graph

22. BELLWORK
How do we calculate average acceleration?

23. 3 - Motion and Forces Key Questions:
What do scientists identify as the fundamental forces of nature?
What happens when there is a net force acting on an object?
What force always opposes motion?
Why is friction sometimes necessary?

24. Fundamental Forces
A Force is defined as any action that can change the state of motion of an object
Gravity, electromagnetic force, strong nuclear force, and the weak nuclear force
Fundamental forces vary in strength
Forces can act through contact or at a distance

25. Balanced and Unbalanced Forces
Whenever there is a net force acting on an object, the object accelerates in direction of the net force
Balanced forces do not change motion
Unbalanced forces do not cancel each other

26. Friction Is a force Always opposes motion
Static friction – occurs between stationary surfaces
Kinetic friction – occurs between moving surfaces
Sliding friction ( usually greater than rolling fiction )
Rolling friction

27. Friction and Motion
Friction is necessary for many everyday tasks to function properly
Non-stick skillets
Cars would not move without friction!!
Can increase helpful friction or decrease unwanted friction
Sand on roads make them less slippery
Lubrication reduces friction

28. Friction and Balance of Forces
Cars do not or do move based on friction
Constant speed
Acceleration
No Slipping

29. Demonstration – Spring Scale
Drag wood and measure the force needed to overcome friction
Friction depends on force applied between surfaces
Rock keeps paper from being blown away by wind
More weight on block  more friction
Rougher surface  more friction