https://youtu.be/Bpid0LBTqWg Unit 7 Matter in Motion https://youtu.be/Bpid0LBTqWg

Objective unit 7 Describe the motion of an object by the position of the object in relation to a reference point. Identify the two factors that determine speed. Explain the difference between speed and velocity Analyze the relationship between velocity and acceleration. Demonstrate that changes in motion can be measured and represented on a graph.

I. Measuring Motion A. Observing Motion by Using a Reference Point Motion is an object’s change in position relative to another object, or reference point. The object that appears to stay in place is called a reference point. The direction of an object’s motion can be described with a reference direction; north South East west Up down

Common Reference Points: The Earths surface is a common reference point for determining motion Trees, buildings, non-moving objects

B. Speed depends on distance and time Speed= distance traveled by an object divided by the time taken to travel that distance SI unit for speed= m/s Other common units= km/h, ft/s, mi/h To determine the average speed= Average speed= total distance total time Actual distance varies from estimated difference b/c the actual is not constant due to weather, traffic, etc…

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C. Velocity : Direction Matters Velocity = speed of an object in a particular direction Speed and velocity DO NOT have the same meaning Velocity looks at direction Speed= 55mi/h but velocity would be 70mi/h north An objects velocity changes if its speed OR direction changes The car can change velocity by going from 55mi/h to 70 mi/h OR by changing directions to East when going around a curve

Resultant velocity= combing two velocities Combing 2 velocities in the SAME direction= add them together Combing 2 velocities in different direction= subtract the velocities

D. Acceleration https://youtu. be/I3GlErUi2q0 Acceleration= rate at which velocity changes Acceleration occurs if speed changes, direction changes, or both Positive acceleration: increase in velocity Negative acceleration (deceleration): decrease in velocity Faster the velocity changes the greater acceleration is Expressed as meters per second per second (m/s/s) or m/s2 Can be graphed as velocity (y axis) vs time (x axis)

7. Calculating Average Acceleration Average acceleration= final velocity-starting value time it takes to change velocity Plane passes over point A at a velocity of 240m/s north. 40 seconds later it passes over point B at a velocity of 260m/s north. What is its average velocity?

Graphing acceleration Time in second (s)