What do you think

the word MOTION means?

Can you define the word motion without using the word MOVE?

Consider the following:1. How do you know the object

moved?

2. What evidence do you have the object moved?

3. How would you describe the object’s movement to someone who wasn’t here to see it?

By comparing the position of an object against an object that is staying in place.

The object that appears to stay in place is a reference point.

When an object changes position over time relative to a reference point, the object is in motion.Displacement is defined as change in position, or final position - initial position.

Direction is important

Distance/Displacement

To test your understanding of this distinction, consider the motion depicted in the diagram below. A physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North. (X1+X2+…=D or Xf-Xi=D)

Even though the physics teacher has walked a total distance of 12 meters, her displacement is 0 meters

Definition of Motion: Change in position

Definition of Reference Point: The point on an object used to determine its position and change of position.

1)Distance

2) Time interval

Definition of Distance (d): The amount of change in position

Formula to calculate distance (d) when initial and final positions are know

d = xf - xi

Definition of Time Interval -- How long it takes for something to happen

Formula to calculate a time interval

Δt = tf – ti

Delta (Δ ): (The Greek letter that means) change

Subscript i: Starting or initial

Subscript f: Final or ending position

Karen walks 2 km from her house to the store . If she leaves the house at 1:00 PM and she arrive at the store at 1:30 PM, how far did she travel and how long, in minutes, did it take for her to arrive at the store.

How Far = distance traveled

How Long = time interval

How Far = distance traveledFind Distance d = xf - xi

xi = 0 km d = 2 km - 0 km = 2 kmxf = 2 km

How Long = time intervalFind Time Δt = tf – ti

ti = 1:00 pm Δt = 1:30 PM - 1:00 PM = 30 min.tf = 1:30 pm

What is SPEED?What is SPEED?Definition of Speed (v)-- the distance traveled by an object divided by the time taken to travel that distance

The units of speed are distance per unit of timeExamples:

Miles per hour……………..mi/hrKilometers per hour………km/hr Meters per sec……………..m/s

Average Speed FormulaAverage Speed Formula

v = d/Δt

Speed ExampleSpeed Example

Jack walks 240 meters up the hill to

fetch a pail of water. Jack falls down and tumbles down the hill in 80 seconds. What is the speed of Jack falling down the hill?

Speed ExampleSpeed Example

Jack walks 240 meters up the hill to fetch a pail of water. Jack falls down and tumbles

down the hill in 80 seconds. What is the speed of Jack falling down the hill?

Find

Speed ExampleSpeed Example Jack walks 240 meters up the hill to fetch a pail of water. Jack falls down and tumbles

down the hill in 80 seconds. What is the speed of Jack falling down the hill?

Find Speed v = d/Δt

d = 240 m v = 240 mΔt = 80 s 80 s

v = 3 m/s