1: I can explain how to determine if an object is in motion. 2: I can differentiate between...
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Transcript of 1: I can explain how to determine if an object is in motion. 2: I can differentiate between...
Measuring Motion
Speed, Velocity, and Acceleration
Learning Targets 1: I can explain how to determine if an object is in
motion.
2: I can differentiate between distance and displacement.
3: I can differentiate between speed and velocity.
4: I am able to manipulate and use speed and velocity formulas to solve problems.
5: I can define acceleration.
6: I can use and manipulate the formula for acceleration to solve problems.
What is Motion?
Change in position in relation to a reference point or stationary object
Distance vs. Displacement
Distance follows the actual path Displacement is always a straight line http://maps.google.com/maps?hl=en&
q=Xenia&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.43148975,d.aWM&biw=1366&bih=622&wrapid=tlif136235527620010&um=1&ie=UTF-8&sa=X&ei=TuQzUf6yD8vryAGCm4CYAQ&ved=0CAgQ_AUoAg
Speed Speed is the distance traveled divided
by the time interval during which the motion occurred
Normally, objects do not travel at a constant speed
Average Speed - total distance total time
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Instantaneous vs. Average Speed
Speed Units
Will always be a distance unit / a time unit
› Ex. Cars: mi./h› Jets: km/h› Snails: cm/s› Falling objects: m/s
Calculating Speed What is the speed of a car that travels
30 miles in 2 hours?
How long will it take a car to go 220 miles traveling 55 mph?
If a car is traveling at 35 m/hr for 6 hours, how far will it travel?
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15 mi/hr.
4 hours
210 miles
Graphing Speed
Graphing Speed: Distance vs. Time Graphs
Phoenix
Denver
Graphing Speed: Distance vs. Time Graphs
Speed = Slope = Rise/Run
Rise
Different Slopes
0
1
2
3
4
5
6
7
8
1 2 3 4 5 6 7
Time (hr)
Dis
tan
ce (
km
)
Run = 1 hr
Run = 1 hr
Run = 1 hr
Rise = 0 km
Rise = 2 km
Rise = 1 km
Slope = Rise/Run= 1 km/1 hr= 1 km/hr
Slope = Rise/Run= 0 km/1 hr= 0 km/hr
Slope = Rise/Run= 2 km/1 hr= 2 km/hr
Velocity Velocity is the speed of an object in a
particular direction Imagine two bicyclers leave the same
building at the same time. The both cycle at 10km/hr for 5 minutes. Why don’t they end up at the same place?
Calculating Velocity Same as speed, but also includes
direction Example:
› A plane travels south at 540 miles/hour.› Johnny walks 1 block/ minute towards the
school
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Resultant Velocity The combination of two different velocities
acting at the same time+ =
- =
16 m/s15 m/s 1 m/s
15 m/s 14 m/s1 m/s
Acceleration
Acceleration is the rate at which velocity changes over time› An object accelerates if its speed, direction, or
both change Unit: m/s2
Average acceleration = final velocity – starting
velocitytime it takes to change
velocity
ΔV
Ta
Acceleration and Velocity
As velocity increases, so does acceleration As velocity decreases, so does
acceleration When direction changes, so does
acceleration When there is a constant velocity, there is
no acceleration Increasing velocity - positive acceleration Decreasing velocity - negative acceleration-
deceleration
Acceleration and Velocity
Calculating Acceleration: Example
A roller coaster’s velocity at the top of a hill is 10m/s. Two sec later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster?
Vf-Vo T 26-10 28 m/s/s
ΔV
Ta
Velocity vs. Time Graph Slope is the acceleration. A straight line is
constant acceleration
0
2
4
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14
0 1 2 3 4 5 6
Time (s)
Sp
ee
d (
m/s
)