Today
Video
Notes
Hwk: Practice A
• What did you do over the weekend (no paper needed)
Objective: The Learner Will calculate the displacement of an object traveling at a known velocity for a specific time interval
“Those who mind don’t matter, those who matter don’t mind”

Motion in One-Dimension

• http://www.youtube.com/watch?v=JieOGvLgbfA

• Frame of reference – a system for specifying the precise location of objects in space and time
• Displacement – the change in position of an object
• Displacement = change in position = final position – initial position
• Displacement is not always equal to the distance traveled.
• Can be positive or negative
• Average velocity – the total displacement divided by the time interval during which the displacement occurred
• Average velocity = change in position / change in time = displacement/ time interval

• During a race on level ground, Andra runs with an average velocity of 6.02 m/a to the east. What is Andra’s displacement after 137 s?
• 5 step problem!
• Hwk: pg. 44 Practice A 1-6

• What is the main unit used for…
• Time
• Distance/Displacement
• Velocity
Today
Warm-up
Check Homework
Notes
Finish outline and
Section Review
Objective: TLW calculate the displacement of an object traveling at a known velocity for a specific time interval
“Those who mind don’t matter, those who matter don’t mind”

Motion in One-Dimension

• Practice A

• Displacement = change in position = final position – initial position
∆𝑥 = 𝑥 𝑓
− 𝑥 𝑖
• Displacement is not the same as distance
• SI unit for displacement is the meter

• Does the odometer in your car measure distance or displacement?
• Can you think of a circumstance in which it measures both distance and displacement?

Warm-up
9/25/13
OBJECTIVE: The learner will identify and describe velocity and speed.
• An object goes from one point in space to another. After it arrives at its destination, its displacement is: a) Either greater than or equal to distance b) Always greater than distance c) Always equal to distance d) Either smaller than or equal to distance e) Always smaller than the distance it traveled
‘You can throw in the towel, or you can use it to wipe off your sweat and keep pushing’ Which will you choose TODAY?

• Average velocity describes how fast the displacement is changing. The equation is:
• Is + or – depending on direction
• Where:
• 𝑣 𝑎𝑣𝑔
= average velocity
• ∆𝑥 = displacement
• ∆𝑡 = elapsed time
• The SI unit of velocity is the m/s 𝑣 𝑎𝑣𝑔
=
∆𝑥
∆𝑡

• Speed
• Always a positive number
• Describes how fast a particle is moving
• Velocity
• Positive or negative number
• Describes how fast the displacement is changing
• Both use SI unit of m/s

• The average speed for a trip might be 53 miles/hour
• However, during this trip your instantaneous speed might have been 0 miles/hour at a stoplight……. Or 70 miles/hour on the open road

• The velocity at a single instant in time
• If the velocity is uniform, or constant, the instantaneous velocity is the same as the average velocity
• If the velocity is not constant, than the instantaneous velocity, isn’t the same as average velocity
• And we must carefully distinguish between the two

• Finish Section 1 Outline
• Section Review pg. 47 #1-4

• What is the formula for velocity and what does it represent?
• If Joe travels 50 meters in 4 seconds what is velocity?
• If Danny runs at a rate of 4.9 meters per second and he runs for 25 seconds, how far has he traveled?

• Acceleration is the rate at which the velocity is changing
• We can change the state of motion of an object by changing its speed, its direction of motion, or both
• Units are in distance/time 2 – m/s 2
Acceleration = change of velocity / time interval

• Practice B pg. 49
• A shuttle bus slows down with an average acceleration of
-1.8m/s 2
• How long does it take the bus to slow from 9.0m/s to a complete stop

• Practice B pg. 49 #1-5
• Due Monday. We will check both Practice A and B at that time

• Spend a few minutes looking over formulas and their respective units.
• Don’t forget to add yesterdays formula to your notecard

• What is the acceleration of football that is initially sitting still to 8 m/s in 2 seconds? (5-step)
• Have Section Review and Practice B out ready to grade.
Today
Warm-up/Objective
Check Homework
Practice C
HWK: Practice C #1-4

• In physics the term acceleration applies to decreases as well as increases in VELOCITY
• The brakes of a car can produce large retarding accelerations, that is, they can produce a large decrease per second in the speed. This is often called deceleration.
• Accelerate in the direction of velocity-speed up
• Accelerate against velocity (decelerate)-slow down
• Accelerate at an angle to velocity-change direction

• Another useful formula for finding velocity if acceleration is constant is
V
=V
+ a*Δt
• Units: v= m/s, t= sec, a=m/s 2

• Another useful formula for finding distance if acceleration is constant is d=V
Δt +(1/2)aΔt 2
• Units: v= m/s, t= sec, a=m/s 2

• A racing car reaches a speed of 42 m/s. It then begins a uniform negative acceleration, using its parachute and braking system, and comes to rest 5.5 s later. Find the distance that the car travels during braking.

• Marissa’s car accelerates uniformly at a rate of
+2.60 m/s 2 . How long does it take for Marissa’s car to accelerate from a speed of 24.6 m/s to a speed of 26.8 m/s?
• Objective: TLW calculate and describe final velocity after any displacement

• Another useful formula for finding distance if acceleration is constant is
𝑉 𝑓
= 𝑉 𝑖
2
+ 2𝑎𝑑
• Units: v= m/s, d= m, a=m/s 2

• In physics the term acceleration applies to decreases as well as increases in VELOCITY
• The brakes of a car can produce large retarding accelerations, that is, they can produce a large decrease per second in the speed. This is often called deceleration.
• Accelerate in the direction of velocity-speed up
• Accelerate against velocity (decelerate)-slow down
• Accelerate at an angle to velocity-change direction

• Another useful formula for finding velocity if acceleration is constant is
V
=V
+ a*Δt
• Units: v= m/s, t= sec, a=m/s 2

• Another useful formula for finding distance if acceleration is constant is d=V
Δt +(1/2)aΔt 2
• Units: v= m/s, t= sec, a=m/s 2

Finish Practice C 3 & 4 pg. 53
Practice D #1-4 pg. 55
V f
=V i
+ a*Δt
• d=V i
Δt +(1/2)aΔt 2

• Check Practice C and D
• Sample Problem E
• Homework 
• QUIZ ON FRIDAY!
Objective: TLW identify and solve for velocity after any displacement

• Grade Practice C and D

• A person pushing a stroller starts from rest, uniformly accelerating at a rate of 0.500 m/s 2 . What is the velocity of the stroller after it has traveled 4.75 m?

• We will be doing a lab tomorrow. Make sure that you come to class prepared.

• Imagine there is no air resistance and that gravity is the only thing affecting a falling object.
• An object moving under the influence of the gravitational force only is said to be in free fall
• For free fall, it is customary to use the letter g to represent the acceleration is due to gravity
• The value of -9.8 m/s 2 should be used for the acceleration during free fall due to gravity
• The negative sign in front of gravity indicates the direction gravity is acting -DOWN

• Now consider an object thrown straight up:
• It moves upward for a while
• At the highest point, when the object is changing its direction from upward to downward, its instantaneous speed is zero
• It then falls downward as if it had been dropped from rest at that height
• During the upward part of this motion, the object slows from its initial upward velocity to zero velocity
• The object is accelerating because its velocity is changing (due to the downward pull of gravity)
• How much does its speed decrease each second?

• Gravity is always acting down, or in a negative direction
• Gravity causes the ball to slow on the way up, and speed up on the way down
• Velocity is POSITIVE on the way up and NEGATIVE on the way down
• At the very top of the balls flight, velocity is ZERO for just a moment

• When something is thrown straight upward under the influence of gravity, and then returns to the thrower, this is very symmetric
• The object spends half its time traveling up; half traveling down
• Velocity when it returns to the is the opposite of the velocity it was thrown upward with
• Acceleration is 9.81 m/s 2 and directed DOWN the entire time the object is in the air!

• Computer lab

• Copy the graph below and then draw in what it would look like for a person to walk at a steady pace for 5 seconds to 5 meters. Then show what it would look like for the man to walk to -10 m at a fast steady ready.

• What does a graph of a person standing still look like?
• What does a graph of a person moving away from an observer look like?
• What does a graph of a person moving towards an observer look like?
• How do differences in speed appear on the graph?

• Section Review pg. 59
• Reviews uniform acceleration and velocity vs time graph

• What is the definition of acceleration?
• On the graph below if the Y-axis was velocity instead of displacement what would constant positive acceleration look like?
• What about an object undergoing constant positive acceleration with positive velocity?

• What are the units for the following
• Displacement in the y-direction
• Velocity
• Acceleration
• Time
• Displacement in the x-direction
• Objective: TLW relate the motion of a freely falling body to motion with constant acceleration, calculate displacement, velocity, and time at various points in the motion of a freely falling object.
• “Just keep going. Everybody gets better if they keep at it.” –
Ted Williams

• Imagine there is no air resistance and that gravity is the only thing affecting a falling object.
• An object moving under the influence of the gravitational force only is said to be in free fall
• For free fall, it is customary to use the letter g to represent the acceleration is due to gravity
• The value of -9.8 m/s 2 should be used for the acceleration during free fall due to gravity
• The negative sign in front of gravity indicates the direction gravity is acting -DOWN

• Jason hits a volleyball so that it moves with an initial velocity of 6.0 m/s straight upward. If the volleyball starts from 2.0m above the floor, how long will it be in the air before it strikes the ground?

• Get out your homework from yesterday

• Only grade #’s 1 and 2

• Treat this as a real test. We will come into class tomorrow and grade it.
• If you finish early go through your book and look for definitions and make sure that you know them

1) What is the correct description of any change of position farther to the right of zero?
2) A dog walks from +4 m to +2 m. Which of the following statements is true about the dog’s motion?

• Make corrections together as a class.
• Use a red pen to show some ideas that you need to focus on.
• When finished you are to work on practice test question in the book.