Chapter 10 Motion The BIG idea The motion

Chapter 10: Motion The BIG idea: The motion of an object can be described and predicted Key Concepts: 10. 1: An object in motion changes position 10. 2: Speed measures how fast position changes 10. 3: Acceleration measures how fast velocity changes

While I check your HW: • Turn to page 309 – On a “small” (not too small) piece of paper please select the unit project you would like to work on…

Chapter 10: Motion • 10. 1 An object in motion changes position • 10. 2 Speed measures how fast position changes • 10. 3 Acceleration measures how fast velocity changes

10. 1 An object in motion changes position • Section Concepts: – How to describe an object’s position – How to describe an object’s motion • Give directions to an object in the classroom… • What kinds of information must you give another person when you are trying to describe a location? • Compare the location of the object with the location of another object or place

Position describes the location of an object • Position – the location of a place or object – Often described by comparing an objects position with where you currently are – You need to discuss two locations to describe the position of an object – to compare

Describing a position • Reference point – a location to which you compare other locations • Points on a graph – Latitude: how many degrees north or south a location is from the equator – Longitude: how many degrees east or west a location is from the prime meridian

Measuring distance • The actual distance traveled depends on the path taken, not just the distance from point A to point B • The standard unit of length is the meter (m) = 3. 3 feet (ft) – Also useful: kilometers (1000 m = 1 km) centimeters (1 m = 100 cm)

Motion is change in position • Motion – the change of position over time Horizontal Vertical • (p. 315) A change in position is evidence that motion happened • How does the picture show time passing? • it shows the jumper in a number of different positions between the start and finish • How is the picture different from a snapshot? • a snapshot freezes a single moment in time

Describing Motion • A change in an object’s motion tells you that motion took place – Tells you nothing about how quickly the object changed positions – it’s speed (or, velocity) – Velocity is speed plus direction – A faster object moves farther than a slower moving object would in the same amount of time – Standard unit of measurement for speed/velocity: meters/second • Velocity equals Distance over time: v = d/t • Velocity: meters/second…distance: meters…time: seconds

Relative Motion • Sit still in a chair: are you moving? – Depends on the position and motion of the person observing you • Observer leaves Earth – you are moving! – How an observer sees your motion depends on how it compares with his own motion • Motion is described using the reference point…or “frame of reference” • “frame of reference”: the location of an observer, who may be in motion also

Relative Motion • Picture a student on a moving bus passing a student on the street (p. 317) – The observer on the bus does not see the driver changing position, but the street sign appears to move pass the window – The observer on the street sees the driver changing position along with the bus, but the street sign appears to remain in the same position **All motion is measured relative to an observer’s frame of reference -an object not moving in one frame of reference will be moving in another

Relative Motion • Suppose you are on a train, and you cannot tell if you are stopped or moving. Outside the window, another train is slowly moving forward. Could you tell which of the following is happening? 1. 2. 3. 4. • Your train is stopped, and the other train is moving slowly forward The other train is stopped, and your train is moving slowly backward Both trains are moving forward, with the other train moving a little faster Your train is moving very slowly backward, and the other train is moving very slowly forward All would look the same to you!!! – unless you compared the motion to the motion of something outside the train

Investigate: Changing Position (p. 316) How are changes in position observed? • Lab notebooks: – Follow procedure, make sketches AND graphs (time vs height) of your observations – Answer: “What do you think? ” and “Challenge” – End of Section 10. 1 Review p. 318 # 5, 6