1. NOTES – Physics Motion in 1-Dimension

2. Unit 2 - Kinematics
The part of mechanics which describes motion without regard to the cuase of motion.

3. 2.1 Displacement – change in position
Distance – A scalar quantity that tells us “how much ground” is covered during motion.
B. Displacment – A vector quantity that tells us an objects “overall” change in position.
1. A vector accounts for direction, a scalar does not. Thus a vector can be positive or negative, a scalar is always positive.

4. 2.1 Displacement – change in position
A vector accounts for direction, a scalar does not. Thus a vector can be positive or negative, a scalar is always positive.
The length of a vector indicates its magnitude. Thus, a vector that is longer represents a larger value and a shorter vector represents a smaller value.

5. A. 2.1 Displacement – change in position
3. In this section, motion happens in only 1 dimension…so things can only move in a + (forward) or – (backward) direction. 4. Example #1 Two cars travel from SD to LA which is a total of 120 miles. One takes the 5 FWY and travels a straight distance of 120 miles. The other takes a side route and travels a distance of 220 miles. Even though they traveled different distances, they both have the same displacement.

6. A. 2.1 Displacement – change in position
5. Example #2
If a truck moves from a position of 10 m to 80 m, its displacement is
∆x = xf – xi = 80 – 10 = 70 m
If the truck moves from a position of 80 m to 10 m, its displacement is
∆x = xf – xi = 10 – 80 = -70 m

7. A. 2.1 Displacement – change in position
6. Example #3
If a truck moves from a position of 10 m to 80 m, its displacement is
∆x = xf – xi = 80 – 10 = 70 m
If the truck moves from a position of 10 m to 80 m, then turns around and moves to 50 m, its displacement is
∆x = xf – xi = 10 – 50 = 40 m
and its distance is 110 m.

8. Gappers of Frip
Read the statement about the Gappers of Frip. Look for the variables in the story and identify how they are related:
Focus on 2 variables at a time.
As a group make a list of as many relationships as you can find.
For each variable, identify the unit it will be measured in.

9. Variables
A. Any quantity that can change or cause change. B. How are variable related: 1. Words 2. Equations and Formulas 3. Graphs or Diagrams

10. Variables
3. Dependent Variable Y = 3x = 5 a) In this equation Y is the “dependent variable” b) Y depends on x 4. Independent Variable a) x is the “independent variable” b) x changes first, then Y changes

11. Time
Time is a scalar
In physics, we will measure two quantities on an x-y coordinate system.
Time will be measured on the x – axis
In physics most of the graphs we do will be rates. A rate is any quantity over time.

12. Speed versus Velocity
Speed is the rate that distance is changing Velocity is the rate of change of position (displacement)

13. Types of Velocity
1. Instantaneous Velocity – The velocity right now or at a specific time. 2. Average velocity – The velocity change during the course of the trip. This is the average of all the different speeds. 3. Constant Velocity – The object is moving with the same speed and in the same direction for the whole trip.

14. Graphing Velocity Velocity = Zero Velocity is constant
a. Horizontal line
b. Slope = 0
Velocity is constant
The sharper the slope the higher the velocity
1) Positive slope
If the line is increasing the displacement is positive.
Slope will be positive.
2) Negative slope
If the line is decreasing the displacement is negative.
Slope will be negative.
Slope = constant velocity

15. Graphing Velocity 3. Velocity is changing over time (acceleration)
The line is curved (non linear)
Slope is changing.

16. Speed & Average Velocity Equation
Equations on Board
Example Prob #1 - What is the speed of a car that travels 50 m in 20 s?
Ex #2 – Find the distance a car travels if its velocity is 30.0 km/hr and it travels for 1.5 hrs.
Ex #3 – On Board

17. Velocity versus Time Graphs
If velocity is constant the graph will be a horizontal line.
Remember positive (+) direction is positive velocity, negative direction (-) is negative velocity.
If line “crosses” x-axis, the object has turned around is going the other direction.

18. Velocity versus Time Graphs
4) We can find the change in position (displacement (X)) from a velocity graph. a) Area under the graph equals change in position. b) the Area = Bh c) if the graph is negative then the height (h) is negative, the area will be negative and the displacement will be negative.

19. Acceleration Acceleration is a change in velocity over time.
Speeding up – acceleration is in the same direction as velocity
Slowing down – acceleration is in the opposite direction as velocity.
Change of direction – is acceleration even if the velocity is constant.

20. Acceleration
2. Acceleration like velocity is a vector. a. Acceleration has a direction, it is either with the velocity or opposite the velocity. b. If acceleration and velocity are in the same direction then an object speeds up c. if they are in opposite directions then an object slows down. d. The sign on the acceleration is the same as for velocity, is the arrow in the positive or negative direction.

21. Displacement, Velocity, and Acceleration Graphs
Trends to note with slope:
1) Horizontal line, slope is zero
2) Sloped line is constant
3) Non linear (curved) graph, slope is changing
 See Board

22. Acceleration Equation
Average Acceleration – See Board
Instantaneous Acceleration