1. Physics Chapter 2 Section 1
Motion in One Dimension
Straight line motion

2. Frame of Reference
For now: a coordinate system (usually a set of axes) used to measure the precise location of an object in space.

3. Distance is NOT displacement
Displacement- the change in position of an object.
For motion in the x or y-direction, it is represented by x or y, respectively.
Distance which refers to how far has something traveled during its motion.
Displacement refers to how far an object is away from where it started; it is the object's overall change in position.
What is the difference between these terms?

4. ∆x = xf - xi The change in x = final position – initial position.
y can also be used depending on the axis
Displacement can be POSITIVE or NEGATIVE

5. Speed and Velocity
average speed = total distance traveled/ time of travel.
Speed can never be negative because the distance traveled does not have a direction associated with it. Speed is a scalar quantity - it is not dependent on direction
A VECTOR must have both magnitude (size) and direction. Velocity is a vector quantity.

6. AVERAGE VELOCITY vavg = ∆x/ ∆t = displacement/ change in time
Average velocity can also be + or – depending on the sign of the displacement. (Obviously time will always be +. )
With velocity you know how fast you’re going and in what direction.

7. Graphing Velocity
An object moving with constant velocity will be a straight line graph of position vs. time.
Average velocity can be determined by drawing a straight line between two points on the graph and finding the slope of the line.
slope = rise/run
Instantaneous velocity –the velocity of an object at an instant in time.

8. Home Fun
Pg 44 q 1-6
pg 47 q 1-6
pg 69 q 1-5

9. ACCELERATION aavg = Δv/ Δt
Acceleration is the rate at which an object changes its velocity.
Acceleration has a direction associated with it and thus is a vector.
Units for acceleration: (distance/time)/time = m/s2

10. Acceleration can be + or -
Acceleration can be + or -. A negative acceleration is commonly referred to as deceleration. HOWEVER- a negative acceleration does not always mean an object is slowing down.
+ acceleration = velocity is increasing in the + direction
decreasing in the - direction
- acceleration = velocity is increasing in the – direction
decreasing in the + direction
IN GENERAL: If an object is slowing down, then its acceleration is in the opposite direction of its motion.

11. Try this:
A police officer turns on his lights as you are traveling km/h. You decide that he would like to speak to you and it takes you 20.00s to come to a complete stop. What is your acceleration in m/s2?
-1.675m/s2

12. Home fun
Pg 49 q 1-5

13. Accelerations occur as either:
Constant Acceleration- A change in velocity by the same amount each second. AKA uniform acceleration.
Accelerations occur as either:
a constant acceleration a non-constant acceleration
in which the velocity changes In which the velocity changes
by a constant amount each by a differing amount each
second second.
Time
(s)
Velocity
(m/s) 1 2 4 3 5 7
Time
(s)
Velocity
(m/s) 1 4 2 8 3 12 16

14. Important equations for uniform accelerations:
∆ x = ½ (vi + vf) ∆ t to find displacement
vf = vi + a ∆t to find velocity
∆ x = vi∆t + 1/2a(∆t) to find displacement
vf2 = vi2 + 2a ∆x to find final velocity
And don’t forget that these can be rearranged for more physics fun

15. Learning to Read Verbal Clues
Problems will often give you variables like t or x, and then give you verbal clues regarding velocity and acceleration. You have to learn to translate such phrases into kinematics-equation-speak:
When They Say . . .
They Mean . . .
starts from rest
vi = 0
moves at a constant velocity
a = 0
comes to rest
vf = 0

16. Home fun
Pg 53 q 1-5
pg 55 q 1-4
pg 58 q 1-6

17. 2-3 FALLING OBJECTS
-9.81m/s2 The force of gravity acting on any object at 1 ATM pressure.
Free Fall – The motion of an object falling with a constant acceleration.

18. Throwing Up
An object that is thrown upward has an acceleration of ______?
-9.8m/s2
At the top of its flight the acceleration is ___________ and the velocity is _______________?
-9.8m/s2 and 0 m/s
Makes calculations easy and fun!!

19. Try these:
The famous Gateway to the West Arch in St. Louis, Missouri, is about 192 m tall at its highest point. Suppose Sally, a stuntwoman, jumps off the top of the arch. If it takes Sally 6.4 s to land on the safety pad at the base of the arch, what is her final velocity? What is her average acceleration?
vf = –6.0 × 101 m/s
aavg = ∆v/∆t = –9.4 m/s2 

20. When it was completed in 2002, the International Financial Center in Taipei, Taiwan, was the tallest building in the world. Suppose a construction worker on the top-most floor of the building accidentally knocks a wrench off a ledge. The wrench hits the ground below 9.56 s later. What is the distance between the top-floor of the International Financial Center and the ground. Assume there is no air resistance.
∆y = 448 m

21. HOME FUN
PG 64 q 1-6
pg 65 q 1-6