Chapter 11 Motion Section 1 - an object s change in position relative to a reference point. Observe objects in to other objects. international unit for. Frame of Reference Frame of reference- a system for specifying the in space and time. Object that you assume is Normally you think of walls or signs as not moving, or as being The perception of motion frame of reference Objects is in when object position with respect to a. What do you use as your frame of reference most of the time? Displacement Displacement-. Speed Always includes Shorter than distance How do you describe motion taking place? To describe motion you is the an object travels per unit of. Calculating Speed To calculate its speed you divide the distance it travels by the time it travels Speed (S) = (d) / the amount of it took (t). Problem: If I travel 100 kilometer in one hour then I have a speed of Problem: If I travel 1 meter in 1 second then I have a speed of. Speed = Problem: If a runner travels 100 m in 10 seconds what was his average speed? Probably not Can solve for the other pieces too Distance = x Time =
Problem: I travelled 25 km in 10 minutes. How many meters have I travelled? Practice Problems: Speed 1. A car race is 500 km long. It takes the winner 2.5 hours to complete it. How fast was he going? 2. It is 320 km to Las Vegas. If you average 80 km/hr, how long will it take you to get there? 3. You are going on a trip. You average 80 km/hr for 6 hours. How far did you go? Constant speed A moving object that it s speed travels at constant speed Constant speed means are covered in an Suppose you and a friend want to run around a track at constant speed for half an hour Average speed Speed is usually Ex. Cars stop and go regularly Runners go slower uphill than downhill = total traveled/total time it took. Calculating Average Speed To calculate average speed figure out traveled and divide by total time it took. Problem 1: It took me 1 hour to go 40 km on the highway. Then it took me 2 more hours to go 20 km using the streets. Total Distance: Total Time: Ave. Speed: Problem 2: I ran 1000 m in 3 minutes. Then ran another 1000 m uphill in 7 minutes. What is my average speed?
Velocity An objects speed doesn t indicate all there is to know about its Velocity the and of an object. Example: An airplane moving A missile moving towards you at 200 m/s People often use the word Speed tells how Velocity tells both in some direction, Velocity is a more term for describing motion Example: Meteorologists use wind velocity measurements to help predict weather Is both speed and direction. 40 km/hr = (only speed) 40 km/hr west = (both speed and direction) Can change velocity two ways Change directions Graphing Speed: Distance vs. Time Graphs
Section 2 Acceleration Any is acceleration, even if the of the object remains the same. When ever an object changes how it moves,. A change in is a change in velocity, and acceleration. Acceleration Types of acceleration Increasing speed Example: Car speeds up at Decreasing speed Example: Car down at stop light Changing Direction Example: Car takes turn (can be at ) Problem: How can a car be accelerating if its speed is a constant 65 km/h? Calculating Acceleration If an object is moving in a straight line Calculate acceleration by figuring the difference in from initial velocity and then divide by. Units of acceleration: Problem: A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver s average acceleration? Graphing Acceleration Can use 2 kinds of graphs Speed vs. time Distance vs. time Graphing Acceleration: Speed vs. Time Graphs Speed (m/s) 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 Time (s) Draw Distance vs. Time
Understanding the formula o Acceleration= final velocity- starting velocity o Change in velocity = - o Acceleration= change in velocity time Motion in a circle An object moving in a circle or a curve is. = acceleration towards the center of the circle.