Transcript File
Week 1 Students will be able to: › Describe motion › Identify a frame of reference › Calculate speed and velocity › Identify the similarities and differences of speed and velocity. Motion was classified in two ways › Natural Movement either up or down Heavier objects fall faster than light Required no force (no push or pull) › Unnatural All other movement Require a force applied Legend says dropped two items from the Leaning Tower of Pisa and observed they fell at the same rate without air friction. Changes to understanding of motion › Objects require a force to start moving › Objects that are moving stay moving › Objects at rest will remain at rest-Inertia Galileo gave more meaning to the word speed than just fast or slow. He took into account the idea of distance covered in a certain amount of time. Defined Speed as distance per unit of time. Formula Speed= Distance/Time It is a scalar quantity-no direction is required Broke into three types › Constant Speed-The speed is fixed and does not change. › Instantaneous Speed-The speed at any instant. › Average Speed-The speed for an entire trip taking into account any changes that occur. Total distance divided by total time. If a car travels 400m in 20 seconds how fast is it going? You need to get to class, 200 meters away, and you can only walk in the hallways at about 1.5 m/s. (if you run any faster, you’ll be caught for running). How much time will it take to get to your class? 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? Speed with a given direction Velocity is a VECTOR quantity › Requires both a magnitude and a direction › Magnitude is the amount (12 km/hr, 3 m/s, 505 cm/min) › Direction: North, South, up, down, left › Examples: 12 km/hr down and 3 m/s north Constant Velocity - means the speed and the direction does not change Remember with velocity if either speed or direction change so will the velocity. What does that mean if you are traveling in a circle traveling at the same speed? › Your speed does not change › Your direction is constantly changing › So… Your velocity is changing Net Force (Velocity) is the result of all components acting on an object. › Vectors in the same direction are added › Vectors in opposite direction are subtracted. What does that mean? › Everything is moving › The earth is rotating and revolving and so is everything on it. › How do we determine what is moving and what is staying still? We need to assign something stationary - frame of reference. Jessica jogs on a path that is 25 kilometers long to get to a park that is south of the jogging path. If it takes Jessica 2.5 hours, what is her velocity? Used to determine movement between two objects › One stationary › One moving It is relative to who is making the observation. › Think about passengers in a car to each other verse someone on the side of the road. The most common Frame of reference is the earth. You are standing on the platform watching the train move from left to right. To you it looks as if the boy is moving from left to right, because relative to where you are standing (the platform), he is moving. According to the boy, and his frame of reference (the train), he is not moving. › A frame of reference must have an origin (where you are standing on the platform) and at least a positive direction. The train was moving from left to right, making to your right positive and to your left negative. If someone else was looking at the same boy, his frame of reference will be different. For example, if he was standing on the other side of the platform, the boy will be moving from right to left.