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
Speed: Distance travelled in a certain time period D S t

9. 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 S t

10. Motion
When an object changes position with respect to a frame of reference, the object is in motion
Velocity: Displacement in a certain time period D V t

11. Bellwork – 09/18/15 Slope of a distance vs. time graph equals speed
What is the speed of the horse?

12. Graphing Motion Slope of a distance vs. time graph equals speed
Slope of a position vs. time graph equals velocity
Constant slope ( straight line ) means constant ________
Changing slope means changing __________ or the object is _____________

13. Graphing Motion
Sometimes easier to analyze motion on graphs

14. 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?

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

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

17. 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?

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. BELLWORK
What changes when acceleration occurs?

20. 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?

21. Calculating AccelerationV A t

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

23. 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

24. BELLWORK
How do we calculate average acceleration?

25. Bellwork – 9/20/16
What always opposes motion?
Friction

26. - 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?

27. 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

28. Balanced and Unbalanced Forces
Whenever there is a non-zero 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

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

30. 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

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

32. Mass and Weight Mass is a property of matter
Weight is a force due to gravitational pull on an object’s mass
Feel weightless in space but still have mass
Weight is related to gravity, but not a fundamental force

33. Demonstration – Spring Scale
Drag wood and measure the force needed to overcome friction ( various scenarios ):
1] single block of wood, wood-side down
2] single block of wood, sandpaper-side down
3] add another block to scenario #2
4] add something else to blocks ( your choice )

34. Questions What two factors appear to affect friction?
What would make this experiment more conclusive ( or how would you be more confident in your data ) ?

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