Kawameeh 8 th Grade Science

 Reference Point - The starting point you chose to describe the location, or position of an object. Position - An object’s distance and direction from a reference point. A complete description of your position includes: 1.A distance 2.A direction 3.A reference points

 An object’s position is its in a certain from a reference point. Suppose your reference point changes… The description of the position will because the reference point is different, however the actual position change at all. distance direction change will not

 Sometimes the terms and are used to determine reference direction. positive negative

 A plus sign ( + ) indicates movement  A minus sign ( - ) indicates movement in the direction of the reference point. in the direction opposite of the reference point.

If the reference direction is EAST Anything moving in the direction toward the EAST would be Anything moving in the opposite direction would be POSITIVE NEGATIVE

 A vector is a quantity in which two things must be specified: 1. Distance from the reference point 2. Direction from the reference point

 A dimension is when distance or length is measured in direction. If you were to describe a position in two directions you would be using one two dimensions

 Reference Directions in two dimensions: North South East West Forward Backward Up Down Left Right

 Motion - the process of changing position. How can you tell the boat moved? What if the fishing pole was the reference point? What if the buoy was a reference point?

Distance - Displacement - The total length of the actual path from start to end. the difference between the initial (first) position and the final position of an object. (straight line) When would distance and displacement be the same? When an object moves in a straight line in one direction.

 Direction of displacement is the direction from start point to end point  Size of displacement is the distance from the starting point to the ending point.

 Speed, velocity and acceleration describe how an objects position and motion change through time.  Rates measure change in something over a length of time.

 Speed - A measure of the distance an object travels per unit of time. How could we increase an objects speed? Move ~3 seconds for a distance of ~3meters Move ~3 seconds for a distance of ~7meters Move ~5 meters in ~5 seconds Move ~5 meters in ~2 seconds

By increasing the distance the object travels in the same time. Or By decreasing the time it takes for an object to travel the same distance.

Speed (S) = distance object travels time it takes to travel distance MeasuringUnitAbbreviation Distancemeterm Distancekilometerkm Timesecondss Timehourshr S= d t

STEP 1 STEP 2 STEP 3 STEP 4 Write the formula Plug in the information that you are given Solve the answer Add your units STEP 5 Add your direction (when solving for velocity only!)

Calculate the speed of a car going 80 meters in 20 seconds.

A girl runs 25 meters in 10 seconds. What is her speed?

 If you know any two of the variables, you can calculate the missing variable.

The rate of change of position in which the same distance is traveled each second.

What distance has the car traveled at 2s? How long will it take the car to travel 132m?

Average speed = total distance total time traveled S = t d tt

Solve the average speed: Melissa shot a model rocket 360 m into the air. It took the rocket 4s to fly that far. What was the average speed of the rocket?

Speed at a specific instant in time. When driving in a car you often change speed. What object in the car tells you your instantaneous speed? Speedometer

 Determine the velocity of a football being thrown 75 meters in 5 seconds toward the east.

 The speed and direction of a moving object. How is velocity represented? The length of the arrow indicates the objects A greater speed is shown by SPEED A LONGER ARROW The arrow should point in the direction of THE OBJECTS MOTION

NO – they are both walking the same speed because the arrow’s are the same length, however their direction is different therefore the velocity is NOT the same

3. When BOTH the speed and direction change 1.When speed of an object changes 2. When direction that the object moves changes

 A measure of the change in velocity during a period of time.

3. Change in direction (EVEN IF AN OBJECT IS TRAVELING AT A CONSTANT SPEED)  An object accelerates when its velocity changes as a result of: 1. Increasing speed 2. Decreasing speed

 Shows how changes over time  X axis =  Y axis = SPEED TIME SPEED

The speed is zero and does not change Horizontal line (like a distance – time graph y = 0 )

The line will be HORIZONTAL The further the line is from the the it is moving. X - AXISFASTER SPEED

The line on a speed – time graph is to the x-axis in the of the time period when it has a speed. The line slants toward the right side of the graph as the speed. CLOSER BEGINNING LOWER UPWARD INCREASES

When initially starting to slow down the point representing speed is from the x-axis. As speed the points representing speed get to the x-axis. The line on a speed-time graph slopes to the right. When the line touches the x-axis, the speed is and the object stopped. FAR DECREASES CLOSER DOWNWARD ZERO

Objects at Rest

Constant Speed

Speeding Up

Slowing Down