Driving “Circular Motion”

1. Task Procedure Evaluation Conclusion Teacher’s Page Driving“Circular Motion” Introduction: While you were driving, have you ever felt like you would fly out of your vehicle as you are going around a turn if the door was not there? Find out why when you discover the difference between centrifugal and centripetal forces. Grab a paper and pencil and let’s get started!!

2. Figure out the difference between Centripetal and Centrifugal Force. • Find the average mass of your favorite type of vehicle and round it to the nearest 100kilograms. • Pick a velocity at which you would like to go around a turn. (as a multiple of 5m/s) • Figure out the force exerted on the car as you take the turn. • Find the force keeping the car on the road. (gravitational force, use g=10m/s^2) • Does your vehicle stay on it’s wheels or flip over and fly off the road? (Write the mass and velocity(speed) your use on top of your paper) Task

3. Read about Centripetal and Centrifugal Force. Decide which force you are solving for. • Pick your favorite type of vehicle, what is the average mass of that type? (for a car use 3000lbs, SUV 4000lbs, truck 5000lbs) • Use a unit converter to put the mass in kilograms (round to nearest 100kilograms). Use the equation w=mg where w is the weight, m is the mass, and g is the value of gravity. • Pick a velocity and convert it to m/s (round to nearest 5m/s) • Find the force exerted on the car as you take the turn in Newtons (N) using the equation Fc=(mv2)/r, where m is the mass of the car, v is the velocity/speed of the car, and r is the radius of the turn (use r=10m). • Find the force keeping the car on the road in Newtons (N). Use the equation Fg=mg. (Hint: you already have this number) • So, does your car flip or make the turn? Procedure

4. Hand in the paper used to solve the force problem. At the top of this paper write either “Centrifugal” or “Centripetal” as the force you have just solved for. • You’ll be evaluated on correctness of the problem and labeling the force correctly. And for stating if your vehicle stays on the road or not. Evaluation

5. “Centrifugal force” isn’t a real force but a misconception. It is just a label for what you think you are feeling as you go around a turn. The fact is that it the centripetal force that you feel that actually acts towards the center of the turn. The “centrifugal force” is the label for the outward feeling that seems to perceived. • Now look at this!! Fc=(mv2)/r and Fg=mg and the tipping point would be where Fc=Fg. So if you set these two equations together you get; (mv2)/r=mg and the m in both equations cancel out. The mass of the vehicle has nothing to do with whether it flips or not!!! Pretty Cool! So, if v>(gr)1/2then you will flip but if v<(gr)1/2 then you won’t. However if v=(gr)1/2 your guess is as good as mine for what happens; depends how lucky you are! • Bonus 1: Use the newly found parameters above and plug in g, r, and v to see if you get the same result. i.e. Flip or not? • Bonus 2: Now that you know what force is at play when dealing with circular motion, can you name other places/things that involve circular motion? Conclusion

6. Objective: Students will relate centripetal force to real life through solving the car problem. They will calculate the centripetal force on the car going around a turn and specify whether the car completes the turn or not. The students will review the given sights to get a better understanding on centripetal and centrifugal forces. The students will hand in their results to be evaluated for correctness and comprehension. • PA- Pennsylvania Academic Standard • Subject : Science and Technology • Area 3.4: Physical Science, Chemistry and Physics • Grade 3.4.12: Grade 12 • Standard C.: Apply the principlesof motion and force. • •Analyze the principlesofrotational motion tosolve problems relatingtoangularmomentum, and torque. • •Interpret a modelthatillustratescircular motion and acceleration. • CRAP Test – Site evaluations Teacher’s Page