Chapter 1: Motion Section 1: Describing and Measuring Motion How do you recognize motion?

1. Chapter 1: MotionSection 1: Describing and Measuring MotionHow do you recognize motion? • An object is in motion when its distance from another object is changing • Movement depends on your point of view

2. What is a reference point? • A place or object used for comparison to determine if something is in motion • An object is in motion if it changes position relative to a reference point

3. What is the basic unit of length? • The meter – a little longer than a yard

4. What do scientists use to measure the length of an object smaller than a yard? • A centimeter – one hundredth of a meter, so there are 100 centimeters in a meter • A millimeter – There are 1,000 millimeters in a meter

5. How do scientists measure long distances? • The kilometer – There are 1,000 meters in a kilometer

6. How do scientists calculate speed? • Speed – the distance the object travels in one unit of time • Rate – tells you the amount of something that occurs or changes in one unit of time • Speed = distance time

7. What is constant speed? • If the speed of an object does not change, the object is traveling at a constant speed

8. What is average speed? • Most objects do not move at constant speeds for very long • To find average speed divide the total distance by the total time • Car trip

9. What is Velocity? • Speed in a given direction • When you know the speed and direction of an object’s motion, you know the velocity of the object • Example 15 km/hour westward

10. How do you graph motion? • You can show the motion of an object on a line graph in which you plot distance against time • Time is along the x-axis and distance on the y-axis

11. How do you interpret motion graphs? • A straight line indicates a constant speed • The steepness depends on how quickly or slowly the object is moving • The faster the motion the steeper the slope

12. Section 2: Slow motion on Planet Earth • According to their explanation, known as the theory of platetectonics, Earth’s plates move ever so slowly in various directions

13. How fast do plates move? • Some small plates can move as much as several centimeters per year, whereas other move only a few millimeters per year

14. How can you calculate the distance an object has moved? • Rearrange the speed formula • Distance = Speed x Time • Converting units – choose a conversion factor that will allow you to cancel units

15. Section 3: AccelerationWhat is Acceleration? • The rate at which velocity changes • In science, acceleration refers to: • increasing speed • decreasing speed • changing direction

16. How do you calculate acceleration? • To determine the acceleration rate of an object, you must calculate the change in velocity during each unit of time • Acceleration = Final velocity – Initial velocity Time

17. How do you interpret graphs to determine acceleration? • The acceleration at any moment is equal to the slope of the velocity time graph at that moment in time Acceleration vs. Constant speed

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