Calculating Speed/Velocity & Using Motion Graphs Chapter 9.2 & 1. 5 The meaning of miles per hour

I. Calculating Speed & Velocity  In other words, you need a formula Speed/Velocity Formula: speed = distance ÷ time Or speed = distance/time To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance. Velocity = speed in a given direction

Instantaneous Speed Examples - Average Speed Examples -

I. Calculating Speed/Velocity Because most object do not travel at a constant speed or velocity, we usually calculate the average speed. Average speed equals the total distance traveled divided by the total time of the trip. Or

V ave = 100 mi = mi/hr 3 hrs

II. What else can we calculate with this formula? Distance – if you know the average speed and how much time you have, you can calculate how far something will travel. Distance = Speed x Time

Distance = speed X time D = (12 mi )(.3 hr) hr D = 3.6 mi

III. One more thing we can calculate with the formula Time – if you know average speed and have a known distance, you can calculate how long it will take to get there. Time = Distance/Speed How long will it take to run 6 km if your average running speed is 4 km/hr? Time = 6km 4km/hr Time = 1.5 hrs

IV. An Easy Way to Remember the Formulas The Magic Triangle! D ST S T Cover up the variable you are solving for. The other 2 are in the right position for the formula.

V. Plotting a Line Graph Chapter 1 Introduction to Physical Science * Write the 6 steps

VI. Slope The slope of a graph line tells you how much y changes for every change in x. Chapter 1 Introduction to Physical Science Slope = rise/run Slope = (y 2 – y 1 )/ (x 2 – X 1 ) For distance vs. time problems, slope = average speed

VII. Using Graphs to Identify Trends Chapter 1 Introduction to Physical Science Line graphs are powerful tools in science because they allow you to identify trends and make predictions. On a distance vs. time graph you can use the slope to find the speed at different time intervals and average speed for the whole trip.

Graphing Motion You can use distance-versus-time graphs to interpret motion. Chapter 9 Motion and Energy