2/25-26 Obj: I can apply concepts of physics – energy, work, and efficiency--- to describe motion. What you should have in the ENB: Write down the first three stages of the engineering design process. State Problem: (summary of constraints) Brainstorm: Questions to Consider: How is the amount of mass important (be careful! Algebra!)? How is location of COM important? How torque important? What is the critical amount of torque you need? How are the wheel size/material important? Analysis: (Finalize your design) Daily entries with 4/5 days being one sentence and 1/5 days having a paragraph reflection At least one clear diagram with parts labeled and indication of changes made in successive prototypes. What you will be adding today to ENB: Data / Calculations (next slide)

Hill Climb Analysis for Engr. Notebook Due Fri 2/26 Part I: Determine coefficient of friction 1. Draw an inclined plane. Labe the forces W_parallel, Fs, W_perpendicular, Fn Write formulas Fs=___, W_parallel=, W_perpendicular= 2. We assume that the robot is “on the verge of sliding” Write out the algebra using the formulas above that allows you to get the very simple formula for u involving the angle. Explain each step. 3. Data: ϴ= Calculation: u= Part II. Calculation of the friction at various angles Data: W of bot ____ Calculate all values in table at right. Data: In testing, what angle was your bot able to achieve? Analysis: Compare that to the angle predicted by the data Table. ϴW_paral lel W_perpe ndicular FsW_parallel > Fs ? Should it slide?

U3 Physics Reflection for Engineering Notebook Gear Trains 1. Using your robot, draw a picture of your gear train. Label each gear by teeth. Calculate the mechanical advantage of your bot. Show work. 2. Look back in your data to find the angular speed in RPM of the motor at power level 127. Use the gear ratio above to calculate the angular velocity of your wheels. Linear Motion 3. Using the angular velocity and diameter of the wheel, calculate the theoretical speed of your bot. Friction 4. State the formula for friction, stating clearly what each term stands for. 5. When you double the weight on a flat surface, what should happen to friction?

U3 Physics Reflection for Engineering Notebook Torque and Application to Gear Ratios 6. Define torque. Provide an example of low and high torque. 7. Using the mechanical advantage calculated above, by what factor should the torque change? Hill Climb Reflection 8. Explain the concept of center of mass. 9. Ideally, where should the center of mass be located for maximum friction on a flat surface? Draw an example and non-example and explain below the illustration. 10. Ideally, to climb an incline where should the center of mass be located? Make a diagram to illustrate how the ideal situation regarding COM is different for an incline. 11. Reflect on the algebra done to derive the formula for the coefficient of friction in the hill climb activity. Theoretically, how should the weight of the bot affect its ability to climb hills? 12. In the real world of our competition, how did the weight affect performance? 13. Draw a detailed sketch of your bot, labeling the overall dimensions and important features. 14. Using what you know about physics, make a suggestion for the next prototype. Point out Important features, and use what you have learned about physics to justify the new design.