Physics/Notes 10.2
- 1. SIMPLE MACHINES SECTION 10.2
- 2. SIMPLE MACHINES • How do I define a simple machine? • How do I differentiate between an ideal and a real machine? • How do I define and calculate efficiency?
- 3. MACHINES • Machine: a device that changes the magnitude or direction of a force • Should make things easier • Simple machines: bottle openers, screwdrivers, … • Complex machines: bikes, cars, …
- 4. BOTTLE OPENER • How does a bottle opener work? • A person applies a force up • This is called the effort force, Fe • The opener applies a force to the cap • This is called the resistance force, Fr
- 6. SINGLE PULLEY • Fe = Fr • MA is 1 • Why have a single pulley?
- 7. DOUBLE PULLEY • If we add a pulley, MA goes over 1 • What happens to direction?
- 8. WORK • Work is Fd • There is input work and output work • A machine can increase force but not energy so, … • Wo = Wi • Frdr = Fede
- 10. MACHINES • Maximum efficiency is 100% • Rare • Most machines are made up of a combination of • Levers • Pulleys • Wheel and axle • Incline plane • Wedge • screw
- 11. BASIC MACHINES
- 12. STEERING WHEEL •
- 13. COMPOUND MACHINES • Compound machine: A machine with two or more simple machines linked such that the resistance force of one machine becomes the effort force of the second machine
- 14. COMPOUND MACHINES • The pedal and front gear are wheel and axel • Effort force is rider on the pedal • Turns into resistance force of front gear on chain • This force turns into the effort force of the chain • That turns into the resistance force of the wheel on the road
- 15. BICYCLE •
- 16. EXAMPLE • The rear wheel on a bicycle is 35.6 cm and a gear with a radius of 4.00 cm. When the chain is pulled with a force of 155 N, the wheel rim moves 14.0 cm. The efficiency of this part of the bike is 95.0 %. Find a. IMA of the wheel and gear (for wheel and axis we can use the ratio of the radii) b. MA of the wheel and gear c. Resistance force d. How far was the chain pulled to move the rim 14.0 cm?
- 17. HOMEWORK • Page 272, # 24 - 29