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Motion . Mrs Sedlock Principles of Chemistry and Physics . Motion. How can two people look at an object, and only one see them as moving?. Frame of Reference. Frame of reference – is a system of objects that are not moving with respect to each other. Relative motion. - PowerPoint PPT Presentation
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Motion
Mrs SedlockPrinciples of Chemistry and Physics
How can two people look at
an object, and only one see them as moving?
Motion
Frame of reference – is a
system of objects that are not moving with respect to each other
Frame of Reference
How fast are you moving?
Depends on the frame of reference!
Ex: Imagine our class is on our way to school on a school bus – Relative to each other – we are not moving Relative to the surroundings- we are moving
Relative motion
Distance – is the length of a
path between two points Units : meter (m), kilometer (km),
centimeter (cm)
Distance
Displacement – a straight line
from the starting point to the end point
Displacement and distance are not always the same!!!!
Displacement
Vector – a quantity that has a
magnitude (number representing a size, length or amount) and direction, and is represented by an arrow
The length of the arrow represents the magnitude, the direction the arrow is drawn represents the direction
Vector
Vectors can be added by combining the vector magnitudes and direction
If the vectors are in the same direction you can add their magnitudes
If the vectors are in opposite directions, you can subtract their magnitudes
Vectors
The vector that is the result of
combining vectors is called the resultant vector
Resultant Vectors
One person says that the high school is 5
miles from Mountain Creek, another person says the school is 7 miles. Can both people be right?
Question…
Comparing distance and displacement activity Drawing vectors ws
Speed and Velocity
Finding the perfect racing line is the key to
bobsledding: The driver struggles with a violently shaking bobsled to keep it on the path that gives the fastest time down the run. In turns, the driver must keep the sled high enough to maintain speed but low enough to avoid going extra distance.
Bobsled
Bobsled
Speed is the ratio of the distance an
object moves to the amount of time the object moves Measured in meters per second (m/s)
Average speed – calculated for the entire trip
Instantaneous speed – measured at a particular instant
Speed
speed (rate) = distance time
Speed
Ex: The bobseld track at the Sochi Olympics is 1.814 km in length. If a bobsled carries a
team of four down the track in 32.51 seconds,
how fast is the bobsled traveling? bobsled
Speed Calculation
Average speed = total distance total time
Average Speed Calculation
Ex. While traveling on vacation, you measure
the times and distances traveled. You travel 35 km in
0.4 hour, followed by 53 km in 0.6 hour. What is your average speed? Total distance = 35 km + 53 km = 88 km Total time = 0.4 h + 0.6 h = 1.0 h Average speed = 88 km = 88 km/h
1.0 h
Average Speed Calculation
Your car’s speedometer gives your
instantaneous speed- the rate at which an object is moving at a given moment in time
Instantaneous Speed
Distance-time graph Distance on the y-axis Time (in seconds) on the x-axis The slope of the line on a
distance-time graph is speed
Graphing Motion
Distance-time graph
Distance time graph ws
Velocity- a description of both the speed
AND direction of a motion- and can be represented as a vector
Two or more velocities can be added by vector addition
Velocity
How can something that is
slowing down be accelerating?
Question….
Acceleration- the rate at which
velocity changes – changes in speed, direction or both – can be represented as a vector
Acceleration
acceleration = Change in velocity
time
which means…..
a = final velocity - starting velocity (v2 - v1)time
Acceleration calculation
if the acceleration is a positive
number, the acceleration is increasing (speeding up)
If the acceleration is a negative number, the acceleration is decreasing (slowing down)
Acceleration calculation
My poorly tuned Honda can
accelerate from rest to a speed of 28 m/s in 20 seconds.
What is the acceleration of the car?
Acceleration calculation
The slope of the line of a
velocity – time graph is the acceleration
Acceleration graph
Acceleration graph
Vocabulary you should know:
Frame of reference
Relative motion Distance Vector Resultant vector Speed
Average speed Instantaneous
speed Velocity Acceleration
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