Chapter 1 Motion Section 1 Describing and Measuring
Chapter 1: Motion Section 1: Describing and Measuring Motion How do you recognize motion? l An object is in motion when its distance from another object is changing l Movement depends on your point of view
Position l. A person or object’s location l What must you have in order to identify an object’s l location?
What is the Location of l The cat? l The man? l The water bowl? l The park bench? l The backpack?
Pick one object in this classroom and describe it’s location.
What is a reference point? l A place or object used for comparison to determine if something is in motion l An object is in motion if it changes position relative to a reference point
What is the basic unit of length? l The meter – a little longer than a yard
What do scientists use to measure the length of an object smaller than a yard? l. A centimeter – one hundredth of a meter, so there are 100 centimeters in a meter l A millimeter – There are 1, 000 millimeters in a meter
How do scientists measure long distances? l The kilometer – There are 1, 000 meters in a kilometer
How do scientists calculate speed? l Speed – the distance the object travels in one unit of time l. Rate – tells you the amount of something that occurs or changes in one unit of time l. Speed = distance time
Formula for speed d S (v) t
What is constant speed? l If the speed of an object does not change, the object is traveling at a constant speed
What is average speed? l Most objects do not move at constant speeds for very long l To find average speed divide the total distance by the total time • Car trip
What is the speed of a sailboat that is traveling 100 meters in 120 seconds?
What is the speed of a baseball that travels 49 meters in 2. 4 seconds.
If the distance covered by a jogger is 2541 meters through the park and the time it took to cover that distance was 43. 6 minutes, what was the speed of the jogger?
It takes Amy 0. 25 hours to drive to school. Her route is 16 km long. What is Amy’s average speed on her drive to school?
You need to get to class, 200 meters away and you can only walk in the hallways at about 1. 5 m/s. How much time will it take you to get to class?
In a competition, an athlete threw a flying disk 139 meters through the air. While in flight, the disk traveled at an average speed of 13. 0 m/s. How long did the disk remain in the air?
How far can you get away from your little brother with the squirt gun filled with paint if you can travel at 3 m/s and you have 15 seconds before he sees you?
How far can your little brother get if he can travel at 2. 5 m/s and in 5 seconds you will discover that his squirt gun has run out of paint?
If you shout into the Grand Canyon your voice travels at the speed of sound (340 m/s) to the bottom of the canyon and back, and you hear an echo. How deep is the Grand Canyon at a spot where you can hear your echo 5. 2 seconds after you shout?
CHALLENGE Bill and Julia want to ride their bikes from their neighborhood to school which is 14. 4 km away. It takes Julia 40 minutes to arrive at school. Bill arrives 20 minutes after Julia. How much faster (in meters /second) is Julia’s average speed for the entire trip.
What is Velocity? l Speed in a given direction l When you know the speed and direction of an object’s motion, you know the velocity of the object l Example 115 km/hour west
How do you graph motion? l You can show the motion of an object on a line graph in which you plot distance against time l Time is along the xaxis and distance on the y-axis
How do you interpret motion graphs? l. A straight line indicates a constant speed l The steepness depends on how quickly or slowly the object is moving l. The faster the motion the steeper the slope
How can you calculate the distance an object has moved? l Rearrange the speed formula l. Distance = Speed x Time l Converting units – choose a conversion factor that will allow you to cancel units
l The Section 3: Acceleration What is Acceleration? rate at which velocity changes l In science, acceleration refers to: lincreasing speed ldecreasing speed lchanging direction
How do you calculate acceleration? l To determine the acceleration rate of an object, you must calculate the change in velocity during each unit of time l Acceleration = Final velocity – Initial velocity Time
How do you interpret graphs to determine acceleration? Acceleration vs. Constant speed l The acceleration at any moment is equal to the slope of the velocity time graph at that moment in time
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