Chapter 5 Matter In Motion Section 1 – Measuring Motion pp. 118-123

Reference Point Reference point – an object that appears to stay in place. Stationary reference points (examples) buildings, trees and mountains. Moving reference points (examples) birds and the earth in relation to the sun.

Motion Motion – an object is in motion when it changes in position over time when compared with a reference point. You can describe the direction of its motion with a reference direction (such as north, south, east, west, up, down)

Speed Speed – the rate at which an object moves. Speed depends on distance traveled and the time taken to travel that distance.

Speed = s=d t s=speed (meters/second) d=distance (meters) t=time (seconds) Average Speed equals the total distance divided by the total time. average speed = total distance total time

CALCULATING AVERAGE SPEED Complete Math Focus Problems on p. 120.

Velocity: Direction Matters The speed of an object in a particular direction is called velocity. Speed and velocity are two different terms with two different meanings. Velocity must include a reference direction. v=d t v=velocity d=distance t=time Examples: 25m/s northwest 25m/s down the hall

Velocity: Direction Matters Changing Velocity You can think of velocity as the rate of change of an object’s position. An object’s velocity is constant only if its speed and direction don’t change.

Chapter 5 Calculating Resultant Velocity Measuring Motion

POSITION – TIME GRAPHS

Acceleration Is the rate of change of the velocity(how quickly an object changes its velocity) The faster velocity changes the greater the acceleration is. The change of velocity divided by the change of time.

Acceleration a=Vf - Vi t Acceleration= final velocity – starting velocity time it takes to change velocity

Acceleration a = acceleration vf = final velocity vi = initial velocity or starting velocity t = the time it takes to go from the initial velocity to the final velocity

Examples of Units for Acceleration Acceleration can be expressed in meters per second per second ( m/s/s) Or meters per second squared(m/s2) Or Km/min/sec Or m/min/hr

3 Methods of Acceleration Speeding up (accelerating) Slowing down (decelerating) Turning (changing direction)

IMPORTANT DEFINITIONS Centripetal acceleration – the acceleration that occurs in circular motion.

Recognizing Acceleration on a Graph – See “A Graph Showing Acceleration” on p. 122