Unit 07 “Work, Power, Energy and Energy Conservation” Lab Predicting the Final Velocity of a Car Using the Conservation of Mechanical Energy

Background Information What variable(s) can be calculated to help determine this? Which equation(s) can be used for solve for the calculated variables? What variable(s) are known? What variable(s) can be measured? How?

Background Information Other important information:

Background Information PE i =mgh i KE i = 0 PE f =mgh f KE f = ½mv 2 What variable(s) can be calculated to help determine this? Which equation(s) can be used for solve for the calculated variables? What variable(s) are known? What variable(s) can be measured? How? Final Velocity (Vf) Total Mechanical Energy (ME) ME i = ME f ME = PE + KE V i = 0m/s g = 9.8m/s 2 Δ x flag = 0.01m h i  measure with meter stick h f  measure with meter stick V f  measure time ( Δ t sensor ) with sensor to get velocity PE =mgh KE = ½mv 2 V = Δ x flag / Δ t senor

Background Information Other important information: The Law of the Conservation of Mechanical Energy: Total Mechanical Energy must stay the same unless there is friction. The Law of the Conservation of Energy: Energy cannot be created or destroyed. Only converted from one form to another. Kinetic Energy: Energy of Motion Potential Energy: Energy of Position

Procedure: Part I: 1.Obtain an inclined plane set up, and car. 2.Set up the sensor at point between the top and bottom points (as indicated in class). 3.Place the car at the top of the track, measure the initial height of the car. 4.Record this data ( in meters) in the data table (h initial ). 5.Measure the final height of the car (at the second sensor). 6.Record this data (in meters) in the data table (h final ). 7.Use data to calculate initial mechanical energy and predict the final velocity of the car. m car =0.057kg Part II: 1.Be sure the cord is plugged into the Part A of the sensor, press “A” and “interval” on sensor. Green lights on! 2.Place car at the top of the track (where you measured the initial height). 3.When ready, release the car. 4.Record the time from the sensor at the bottom of the track. Δx=0.01m, the width of the flag 5.Using data to calculate the final velocity of the car. 6.Compare the predicted and experimental final velocity of the car.

Data & Calculations Table: Part I “Predicted Final Velocity”: Initial Height (m) h initial Initial Potential Energy (J) PE i Initial Kinetic Energy (J) KE i Initial Total Mechanical Energy (J) ME i Final Height (m) h final Final Potential Energy (J) PE f Predicted Final Kinetic Energy (J) KE f Predicted Final Velocity (m/s) V f

Data & Calculations Table: Part II “Actual Final Velocity”: Sensor Time (s) Δt Actual Final Velocity (m/s) V f experimental Percent Error (%)

Calculations - Part I: 1. Use the equation ME initial =ME final to predict the final velocity of the car.

Calculations Part II: 1. Final Velocity: V f =Δx/Δt 2. Percent Error: %Error = (V f actual – V f predicted ) x 100 V f predicted

Conclusion Question: 1.Did your predicted final velocity match your actual final velocity? Use the Law of the Conservation of Mechanical Energy to explain. Use data to support your answer.(A.E.S.) 2.Is the total energy conserved in this lab? Use the Law of the Conservation of Energy to explain why or why not. (A.E.S.)