Introduction: People commonly confuse the two words force and pressure. The amount of pressure depends on how a force is distributed over a certain area. It decreases as the area increases and increases as the area decreases. P = F/A =FA In this activity, you will determine the force that each automobile tire exerts on the road. Then you'll add these four forces together to get the total support provided by the tire pressure. This will be the experimental weight of your car. The force from each tire can be found from the equation above by solving for the force. This gives us: F = PA F = Objectives: . To determine an experimental weight of a car within 20% using the tire pressure. a . ⢠To compare the experimental value with the accepted value using a % difference ⢠To make an in-depth analysis of the results Hypothesis: You insert this, it will consist of two parts 1. Your prediction about your success in determining the weight of the car. (this will not involve a guess about numbers, just that you will or will not be able to determine the weight) 2. How close you expect to be stated as a percent error (I give you a target for this one, see objectives) Hypothesis: insert your hypothesis here!! Apparatus: ⢠Car ⢠Tire pressure gauge ⢠Blank paper (graph paper, manila folder, printer paper...) ⢠Ruler or measuring tape ⢠⢠Flat level surface Procedure: 1. Find reasonably level ground (this is for safety and ease of measurement) 2. Park and set the brake of your car 3. Place a piece of blank paper in front of each tire. 4. Move the car so that each tire is centered on the paper. 5. Set brake of your car 6. Trace the outline of the tire where it makes contact with the paper 7. Roll the car off the papers and label each paper as the right front (RF), right rear (RR), left front (LF), and left rear (LR) 8. Measure and record the tire pressure of each tire (RF, RR, LF, and LR) 9. Calculate the area inside the trace in square inches (should be roughly a rectangle so A = ( x w) Record your data in the table 10. Calculate the force due to the tire pressure on the surface for each tire (F=PA). 11. Add the four forces to get the experimental weight of the car. 12. Ascertain the weight of your car from the owner's manual or the metal plate on the driver's side door jam. 13. Calculate the percent difference between your value and the owner's manual value. 14. Are you within 20%? What could account for any excess error? Does the owner's manual value give the actual value of your car's weight? When and how are car weights determined? Does a car weight change over time? What factors about the tires make a difference? What procedural changes could improve accuracy? How could you make a direct measurement of your car's weight? Data: Tire Lengthlin) Widthlin) Areaſin? Plib/in? Force (Lbs) IRF RR ILF LR Weight
