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Energetically Challenged. Maximize your mousetrap potential. Re-cap. Linear Forces: Friction Proportional to Normal force Static Friction opposes relative motion of two surfaces Coefficients of friction found experimentally Rotational Forces: Torque Torque causes angular motion
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Energetically Challenged Maximize your mousetrap potential
Re-cap • Linear Forces: Friction • Proportional to Normal force • Static Friction opposes relative motion of two surfaces • Coefficients of friction found experimentally • Rotational Forces: Torque • Torque causes angular motion • Moment of inertia found for drive axle Wcar N Fs Fs N N T Wmass
Work and Energy • You (120 lb) and a friend (150 lb) go hiking (uphill) after eating ½ of a pizza. • Who will use more energy as they are hiking? • Who will be able to hike farther (higher)? • Why do you make these predictions? • What is the unit of energy that people track? • How is this hiking example similar to your mousetrap car?
Work and Energy • Your heavier ‘friend’ will use more energy: his weight (a force) is higher, so he will use more energy over the same distance. • Because you and your friend start with the same amount of energy (calories from the ½ pizza), you will be able to go farther than your friend.
Energy: Potential and Kinetic • Potential energy: an object at rest • Apple before falling from tree: • Mousetrap arm when trap is set: (calculated from transferred force) • Kinetic energy: an object in motion • Apple falling from tree • Mousetrap car in motion
Putting it together • Energy efficiency can be calculated, improved by analyzing work done by forces • Mousetrap arm • Friction • Torque
Max Your Ride • Follow workbook to calculate efficiency of current model car • Use what you know: past experiments • Propose improvements • Troubleshoot, Redesign, Rebuild!