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