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Simple Machines

Simple Machines. 5.2. SIMPLE MACHINES: ease load, changing either magnitude or direction of a force. WORK input <WORK output FORCE exerted <FORCE machine LEVER Simple Lever Pulley Wheel and axle INCLINED PLANE Simple Inclined Plane Wedge Screw. The Lever Family!. EXAMPLES

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Simple Machines

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  1. Simple Machines 5.2

  2. SIMPLE MACHINES: ease load, changing either magnitude or direction of a force WORK input<WORK output FORCE exerted<FORCE machine • LEVER • Simple Lever • Pulley • Wheel and axle • INCLINED PLANE • Simple Inclined Plane • Wedge • Screw

  3. The Lever Family! EXAMPLES • Claw hammer • Crowbar • See-saw A bar that is free to pivot or turn at a fixed point. -Fixed point=Fulcrum -Input Arm=Distance from the fulcrum to where the input force is. -Output Arm=distance from the fulcrum to the output force.

  4. Three classes • 1st class lever: Claw hammer, the fulcrum is located in the middle of the arm. • 2nd class lever: The fulcrum is located at the end of the arm, output force is b/t input force and fulcrum: A wheelbarrow. • 3rd class lever: The fulcrum is located at an end of the arm, the input force is applied b/t the output force and fulcrum.

  5. Pulleys • Pulleys are modified levers. • Fixed Pulley-change direction of the input force • Movable Pulley- increase input force. • Axel = Fulcrum • Depending on the number and arrangement of pulleys, the mechanical advantage is different. • Fr=Fe Mechanical Advantage =1 w/ 1 fixed pulley

  6. Block and Tackle-System w/ fixed and movable.

  7. Wheel and Axle • Axle in the center of the wheel

  8. Inclined planes • Inclined planes - multiply and redirect forces. • Wedge - is a modified inclined plane • Screw - is an inclined plane wrapped around a cylinder.

  9. Compound Machines • Two or more simple machines

  10. Using Machines • Increase Force • Change Direction • Make Work Easy • INPUT FORCE-Force applied to the machine • OUTPUT FORCE-Applied by the machine • Mechanical Advantage= Ratio Output Force/Input Force • Fresistance/Feffort

  11. Ideal Mechanical Advantage (IMA)=equal to the displacement of the effort force divided by the displacement of the load. Fr/Fe=de/dr • Efficiency (%) = Output Work/Input Work x 100% • MA/IMA x100

  12. Practice Problem: 1.) You examine the rear wheel on your bicycle. It has a radius of 35.6 cm and has a gear with a radius of 4 cm. When the chain is pulled with a force of 155 N, the wheel rim moves 14 cm. The efficiency of this part of the bicycle is 95%. • A. What is the IMA of the wheel and gear: 4 cm/35.6 cm=0.112 • B. What is the MA of the wheel and gear: e=ma/IMAx 100 MA=e/100 xIMA (95/100) 0.112= 0.106 • C. What is the resistance force: MA=Fr/fe Fr=Max Fe 0.106(155)=16.4 • D. How far was the chain pulled to move the rim 14 cm: IMA=de/dr de=IMA x dr 0.112(14)=1.57 cm

  13. 2. A sledgehammer is use dto drive a wedge into a log to split it. When the wedge is driven 0.2 m into the log, the log is separated a distance of 5 cm. A force of 17000 N is needed to split the log and the sledgehammer exerts a force of 11000. • What is the IMA of the wedge? (4) • What is the MA of the wedge? (1.5) • Efficiency? (38%)

  14. Impulse • Average force times time Ns • F=ma….

  15. Momentum • Mass times velocity • Kg m/s • Vector • Impulse Momentum Theorem • Impulse is the change in p • CONSERVATION OF MOMENTUM: • pi=pf

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