S ection 1: Describing and Measuring Motion How do you recognize motion? An object is in motion when its distance from another object is changing Movement depends on your point of view
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
What is the basic unit of length? The meter – a little longer than a yard
Example 1: How many inches are in 1 meter? You must complete this using the long version
Example 2: How many meters are in 1 yard? You must complete this using the long version
two unit conversion example 1. convert 80 km/hr into meters per second
How do scientists measure long distances? The kilometer – There are 1,000 meters in a kilometer
Example 1: How many meters are in 4.5 kilometers? Use both the short and long method
Example 2: How many kilometers are in 8,562m? Use both the short and long method
What is Distance? Scalar Quantity- only tells us the Number or how much Distance-how much ground an object has covered while it is in motion
Examples-distance In the morning on your way to school you walk to pick up your friend at their house which is 4 Km from your house. Then you and your friend walk anther 3 Km to the school. What is the total distance that you and you walked?
5. 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 S peed = distance time
SPEED Speed is a measure of how fast something is moving. It is the rate at which a distance is covered Units of speed could be: km/h, m/s, mi/h, ft/s The SI unit for speed is m/s. d s t
Examples-speed problems 1. A dog runs to a fence 20 meters away. It takes him 15 seconds. What is the dog’s speed? D= T= S= 2. A cross country walker covers 240 miles in at a speed of 16 mi/day. How days does she cover D= S= T=
Examples-time An airplane can fly 600 km/hr. How long will it take the airplane to fly 1500 km? Answer: 2.5 hours
Examples-distance A migrating robin can fly 440 km/day. How far will the bird travel in 25 days? Answer: 11,000 km
What is constant speed? If the speed of an object does not change, the object is traveling at a constant speed
What is average speed? Most objects do not move at constant speeds for very long The Average speed is the speed over the entire trip
Speed Average Speed
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 Sketch graph Time (s)Distance (m)
What is Displacement Vector Quantity - tells us how much (number) AND direction (south, north, east, west) Displacement: the change in the position of an object A plus (+) means positive (forward, up, north) directions; a minus (-) means negative (backwards, down, south) direction
Distance vs. Displacement DistanceDisplacement Straight or curved lineStraight line Not direction specificHas direction
Displacement Formula Δ=______________ i=_______________ f=_______________ Δ X = Xf - Xi
Example You and a friend decide to go for a run. Starting at your friends house you guys jog 2 km to the south and stop at a park. What is your displacement? Givens: Xf= _______ Xi= _______
What is Velocity Velocity s peed in a given direction
What is Velocity? When you know the speed and direction of an object’s motion, you know the velocity of the object Example 15 km/hour westward
Negative velocity means the object is moving in the opposite direction. d. In a car, we can change the velocity 3 ways: 1. Change the speed (faster): 2. Change the speed (slower): 3. Change Directions:
Velocity equation Velocity= Average Speed
Velocity Questions 1. How far does Bob run if he maintains an average velocity of +3 m/s for 10 s?
Velocity Questions 2) Is it possible to go around a corner without changing velocity? Explain.
Velocity Questions 3) One car is going 25 miles/hr north, another car is going 25 miles/hr south. Do they have the same velocity? Explain.