PhET Interactive Simulation Displacement and Velocity The usual rules of arithmetic don’t work when you want to study objects that are not always moving in the same direction. If a car drives 5 miles east and then 5 miles north, its displacement is not 10 miles northeast. The “Vector Addition” PhET shows how to perform arithmetic with two vectors graphically through the use of vector components. Directions Open the “Explore 2D” pane and check the “Values” box. Drag the vector a onto the coordinate grid with its tail at the origin. Select each option in the “Components” pane and note the different ways of representing a vector with a length of 10.0 as the sum of two perpendicular components. Add a second vector (b) to the coordinate grid and modify its appearance so that it has a horizontal component of 8.0 and downward vertical component of –6.0. Move the tail of vector b to the tip of vector a. Turn on the “Sum” box and drag the sum vector (s) so that its tail is at the origin. Select each option in the “Components” pane and notice how the components of the two original vectors are related to the components of the sum. Explain why the sum of two vectors, each with a length of 10.0 m, is not equal to 20.0 m. Develop and Use Your Model SEP Develop Models Use the space below to show how to represent the sum of one vector pointing down and to the left and a second vector pointing down and to the right in terms of the components of the two vectors. SEP Conduct an Investigation Turn off the “Sum” option and see if you can add two displacement vectors that each have a length of 18.0 m to produce an overall displacement of 30.0 m to the right. How could you interpret your drawing as a set of instructions for a person walking from their home to a market?