1. Motion notes
Physical Science

2. Are you moving? Something is in motion if it changing position
Determining whether something changes position requires a point of reference
Frame of reference = a place or object that you assume is fixed.
You observe how objects move in relation to that frame of reference.
Relative motion =how
are you moving relative
to a frame of reference

3. Distance and Displacement
Ex. Suppose you are going to school and you need to be there in 5 mins. Can you get there on time by walking or should you ride your bike?
You need to know the distance you need to
travel and the direction.
You would specify your
displacement

4. Distance
Distance :is a measure of how far an object has moved and is independent of direction.
If a person travels 40m due east, turns and travels 30m due west, the distance traveled is 70m.

5. Displacement
Displacement : has both magnitude (measure of the distance) and direction.
Displacement is a change of position in a particular direction. For example: 40m east is a displacement.

6. Total Displacement
Total or final displacement: refers to both the distance and direction of an object’s change in position from the starting point or origin. Displacement only depends on the starting and stopping point.
Displacement does not depend on the path taken.
If a person travels 40m due east, turns and travels 30m due west, the total displacement of the person is 10m east.
If a person travels 40m east and then travels another 50m east the total displacement is 90m east.

7. Example
Total Distance = 4m + 3m = 7m Displacement = distance of most direct route + direction Displacement = 5m northeast

8. Speed To describe motion: how fast something is moving
Speed = Distance (in meters) S = _D_
Time (in seconds) T
D = S X T
T = _D_ S D T S

9. Example
Ex. Calculate the speed of a swimmer who swims 100 m in 56 seconds. S = d/t S = 100m/56 sec. S = 1.8 m/s *Don’t forget your units!!

10. Average vs Instantaneous Speed
How can you determine a car’s speed if it is always changing?
Ex. Car travels fast on the express way but slows down for a red light.
Answer = Calculate its average speed between where it starts and stops.
The speed of an object at one instant of time is the object’s instantaneous speed.
What is the difference between average and instantaneous speeds?

11. Average vs Instantaneous Speed
Ex. It takes you 0.5 h to walk 2 km to the library.
Your average speed would be as follows:
Speed = total distance/total time taken
S = 2km / 0.5 h
S = 4 km/h
However, your instantaneous speed probably changed throughout your trip. At a crosswalk your speed was 0 km/h, then you sped across the highly traffic street at 7 km/h. Then everywhere else you walked at a steady pace of 4 km/h
A speedometer measures instantaneous speed.

12. Mini -Activity: Speed Walking
Materials
Stopwatch
What To Do
1) The tape on the floor marks 5 meters long.
2) Time how fast you can walk the length of one tape line to the next without lifting your feet from the floor.
3) Repeat three times.
4) Record your data & calculate your average speed.
Moon walking bird:

13. Data Trials Time (seconds) 1 2 3 Average time
Average speed = distance / time

14. Graphing Motion -Time goes on the x-axis - Distance goes on the y axis
You can use a distance-time graph to compare speeds of objects.
What student is the fastest?
_D__
What student is the slowest?
_A__
A steeper line represents a
Greater speed
A horizontal line means no
change in position therefore speed
equals zero.

15. Speed graph
When the line is horizontal on a speed graph the object is not moving.
- Motion of Earth’s crust—so slow we don’t notice
A steady line up is constant speed
Ex. The speed of light is always at constant speed
A curved line up is increasing speed

16. Speed graph
Observe the red line, describe the object’s speed and what it is doing.
Answer:
The line is increasing =
car starts its journey away from home.
The horizontal line =
car stops at a store
The line is decreasing =
car is going home

17. Velocity
Velocity: the speed of an object and the direction of its motion.
Ex. Car is moving west with a speed of 80 km/h or
V = 80 km/h west
The velocity of an object is sometimes represented by an arrow. The arrow points in the direction in which the object is moving.
The velocity can change even if the speed stays constant
Ex. Speed is 40 km/h but direction goes from west to north.

18. Calculating Velocity
Velocity is a vector quantity, it has a direction!

19. Calculating Velocity
In the equation, “v” can represent either velocity or speed and “d” can represent either displacement or distance, depending on the context of the problem.
Speed and velocity video clip 2:36

20. Calculating Velocity
When calculating average velocity using v =d/t: the average velocity equals the total displacement divided by the total time.
The total displacement may be different from the total distance.
* When indicating the average velocity, direction must be given and the average velocity will have the same direction as the total displacement.
The moving man simulation

21. Acceleration
Acceleration = The rate of change of velocity and occurs when an object changes its speed, its direction, or both. -Positive acceleration = speed increases. - Negative acceleration = speed decreases

22. Acceleration
When an object changes speed or direction, it is accelerating.
Examples:
1. Earth is accelerating constantly as it orbits the sun in a nearly circular path.

23. Calculating Acceleration
Calculation for acceleration:
Acceleration = change in velocity (Δ V)
Time
Change in velocity =
Final velocity – Initial velocity
SI units for acceleration = meters/second/second =
m/s2 (meters per second squared).

24. Calculating Acceleration Example
Amusement park acceleration—Roller coasters 1. Changes in speed cause acceleration. 2. Changes in direction cause acceleration.

25. Calculating Acceleration Example
Example: Calculate the acceleration of a bus whose speed changes from 6 m/s to 12 m/s over a period of 3 seconds. A = Δv/Δt A = (sf – si) t A= (12- 6)/ 3 = 6 ÷ 3 = 2 m/s2

26. Graphing acceleration
The motion of an object that is moving in a single direction can be shown with a graph.
Speed is on the y-axis and time is on the x-axis.
From A to B and C to D you will have a positive acceleration
From B to C you have zero change in speed
From D to E you will have slowed down

27. Collisions Collision = when two moving objects collide.
Ex. When a cue ball collides with another ball in a game of pool. What happen?
The collision can change the speed of each ball, the direction of motion of each ball, or both.
The changes of motion depend on their masses and their velocities before the collision.

28. Mass and Inertia Mass = the amount of matter in an object.
The more mass an object has, the harder it is to change its motion.
Ex. You would have to push harder to stop and adult than to stop a child.
Inertia = the tendency of an object to resist a change in its motion
The amount of resistance to a change in motion increases as an object’s mass increases.
Show penny/card/cup demo
Bill Nye Motion and interia 23:16
Questions 
1. To which object was a force applied by the flick and which object was not acted upon by the flick?
2. Why did the penny fall into the cup and not fly off with the index card?
3. What force held the penny in place while the card was flicked out? What force brought the penny down into the cup?
4. Would the penny move in the same way if sandpaper was used instead of the index card?
Summary
The inertia of every object resists the change in motion. In this case, the inertia of the penny held it in place while the index card was flicked out from under it. The force acting on the index card was not applied to the penny. After the index card was moved from under the coin, gravity supplied the force to bring the penny down into the cup. If a force had been applied to both the card and the penny, then both would have moved and the penny would not have fallen into the cup.

29. Momentum
Besides increasing the mass, increasing the speed or velocity makes an object harder to stop.
Momentum = a measure of how hard it is to stop an object
it depends on the object’s mass and velocity.
Represented by p
Momentum (kg ·m/s) = mass (in kg) X velocity (in m/s)
p= m·v
*Since velocity includes a direction, momentum has that same direction

30. Momentum example
Ex. Calculate the momentum of a 14 kg bicycle traveling north at 2 m/s.
p = m · v
p = (14 kg) X (2 m/s)
p = 28 kg · m/s
Bill Nye : momentum 22:56

31. Conservation of Momentum
In billiards when the cue ball hits another ball, the cue ball slows down and may change direction. Meanwhile, the other ball starts moving, so its momentum increases.
In any collision, momentum is transferred from one object to another. The momentum lost by one ball equals the momentum gained by the other ball. The total amount of momentum doesn’t change and is conserved.

32. The Law of Conservation of Momentum
The law of conservation of momentum: the total momentum of a group of objects remains constant unless outside forces act on the group
Only an outside force, such as friction between the billiard balls and the table, can change the total momentum of the group of objects.
Friction causes the balls to slow down therefore momentum will decrease

33. Using Momentum Conservation
After the collision, the total momentum remains the same, and only one object is moving. Its mass is the sum of your mass plus the mass of the basketball. Use the equation to find the final velocity
Total momentum = (mass of girl + mass of basketball) X velocity
10 kg · m/s east = (2 kg + 48 kg) X velocity
10 kg · m/s east = (50 kg) X velocity
0.2 m/s east = velocity
Notice the final velocity is
much smaller.

34. Using Momentum Conservation
Ex. A 48 kg Girl on roller skates at rest, catches a thrown 2-kg basketball at a velocity of 5 m/s east. What is the initial momentum? Total momentum = momentum of basketball + your momentum Pt = 2 kg X 5 m/s east + 48 kg X 0 m/s Pt = 10 kg · m/s east

35. Types of collisions
Masses in these cases are all the same.

36. Types of collisions

38. Motion Bill Nye video on Motion 23:16
Force and motion grinch song 4:21
Friction:
Momentum:
Gravity: 22:55
Buoyancy 22:31
Pressure: 23:08