Science Physics Chapter One

Science Physics Chapter One

1. Lesson 1 Describing Motion

   • An object is in motion if its position changes relative to another object.
     • The place or object used for comparing motion is known as the reference point
   • Motion can change relative to different objects
     • ex.) If you use your chair as a reference point you may not be moving. But if you use the sun as a reference point your moving extremely fast.
   • To describe motion you need to use proper units of measurement
     • Scientists use the International System of Units (SI) for measurements
       • The SI unit for length is meters.
     • Distance is the length of a path between two points

2. Lesson 2 Speed and Velocity

   • The speed of an object is the distance an object travels per unit of time
     • To calculate the speed of an object, divide the distance the object the amount of time it takes to travel that distance
       • Speed=Distance÷time
     • The SI unit for speed is m/s
   • To calculate average speed, divide the total difference travelled by the total time.
   • Instantaneous speed is the speed at which an object is moving at a given instant in time.
   • Speed in a given direction is called velocity.
   • You can show the motion of an object on a line graph in which you plot distance versus time.
     • Time is shown on the x-axis and distance is shown on the y-axis.
     • The steepness of a line on a graph is called slope.
       • The slope tells you how fast one variable changes in relation to the other variable in the graph
       • Since speed is the rate that distance changes in relation to time, the slope of a distance vs time graph represents speed
     • You can calculate the slope of a line by dividing the rise by the run
       • Rise is the vertical distance between any two points on a line
       • Run is the horizontal difference