Lab Manual 2005

Relative Velocity SimulationSituation: Consider two ships at sea that are travelling near each other. The radar operator onone ship can see the other ship on his radar screen. With each sweep of the radar it plotsthe position of the other ship relative to his ship. His ship is located at the center of thescreen. From this information he can easily tell the rate at which the ship is approachinghim. This is known as relative velocity.But does this tell us the other ships actual speed? Does it tell us the actualdirection the other ship is headed? This lab exercise will attempt to give you anunderstanding of the concept of relative velocity and how it relates to actual velocity.Frames of Reference1. Suppose you are on a ship that is moving “forward”. When you look over the side at thewater, which way does it appear to move? (Consider the speed of the water flow and thedirection in comparison to the speed of the ship itself)2. What if you were restricted to only looking at the water flowing along the side of theship? Do you think this observation could accurately give you information about themotion of the ship?3. Suppose you were on a ship that was anchored in the middle of a river, where the currentis very fast. You look over the side and observe the water flow around the ship. Whatdoes it look like?4. Re-examine your answer to question 2. Make any additional comments here.5. Have you ever had your car stopped at a traffic light and noticed the car ahead of you rollback toward you. Did you briefly get the sensation that you are actually moving insteadof the car ahead? While this sensation is happening is there any way of determining forsure who is actually moving?6. Now suppose that in question 5 you are not stopped at a light but are parked on a ferryand as the ferry begins to pull out from the dock the car ahead of you, which wasmistakenly left in neutral, starts approaching you. Compare this situation with question5. Which car is now moving? Is it possible to tell from your observations?- 19 -