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Ch. 10 Energy, Work, and Simple Machines

Ch. 10 Energy, Work, and Simple Machines. Milbank High School. Sec. 10.1. Objectives Describe the relationship between work and energy Display an ability to calculate work done by a force Identify the force that does work

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Ch. 10 Energy, Work, and Simple Machines

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  1. Ch. 10Energy, Work, and Simple Machines Milbank High School

  2. Sec. 10.1 • Objectives • Describe the relationship between work and energy • Display an ability to calculate work done by a force • Identify the force that does work • Differentiate between work and power and correctly calculate power used

  3. Energy • The ability to produce change in itself or the environment • Mechanical Energy • Ability to do work • Potential Energy • Stored energy • Kinetic Energy • Energy of motion

  4. Kinetic Energy • Utilizes motion equations and Newton’s second law of motion • Produces

  5. Work • Transfer of energy by means of forces • 1/2mv1 – 1/2mv0 = Fd so… • K = 1/2mv2 so… • W = Fd or… • K1 – K0 = W or ∆K = W • Measure in Joules (kg·m2/s2)

  6. Problems • Example Problem Pg. 226 • Calculating Work Practice Problems Pg. 227

  7. Calculating work at an angle • W = Fd cos Ө • Example Problem Pg. 228 • Force and Displacement at an Angle

  8. Power • Power is the rate of doing work, or the rate at which energy is transferred • P = W/t • Power is measure in watts (1 joule of energy transferred in one second)

  9. Sec. 10.2 • Obejctives • Demonstrate knowledge of why simple machines are useful • Communicate an understanding of mechanical advantage in ideal and real machines • Analyze compound machines and describe them in terms of simple machines • Calculate efficiencies for simple and compound machines

  10. Machines • Ease the load by changing either the magnitude or the direction of a force as it trasmits energy to the task • Basically….make tasks easier • Wi • work input, the work you do • Wo • Work output, the work the machine does

  11. Mechanical Advantage • The ratio of resistance force to effort force • Fr/Fe • Hopefully its greater than 1 • Effort force • The force you exert on a machine • Resistance force • Force exerted by the machine

  12. Ideal Mechanical Advantage • Ideal Machine: all energy transferred, or in other words W0 = Wi Ideal Mechanical Advantage = de/dr Measure distances….with MA, you measure the forces

  13. Efficiency • An ideal machine has equal output and input • Dpes it really ever happen? • Efficiency can be defined as W0/Wi x 100 (for a percent) • Or…MA/IMA x 100 • Efficient machines have an MA close to the IMA

  14. Simple Machines • Lever • Pulley • Wheel and Axle • Inclined Plane • Wedge • Screw

  15. Compound Machines • Consists of two or more simple machines • The resistance force of one becomes the effort force of the other • Example Problem Pg. 237 • Bicycle Wheel

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