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Work and Energy

Work and Energy. Ch. 9.2 Simple Machines. Section 9.2 Objectives. Name and describe the six types of simple machines. Discuss the mechanical advantage of different types of simple machines. Recognize simple machines within compound machines. Simple Machines.

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Work and Energy

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  1. Work and Energy Ch. 9.2 Simple Machines

  2. Section 9.2 Objectives • Name and describe the six types of simple machines. • Discuss the mechanical advantage of different types of simple machines. • Recognize simple machines within compound machines.

  3. Simple Machines • A machine is any device that transmits or modifies force. • All machines are combinations or modifications of six simple machines (divided into two groups). • The Lever Family :Lever, pulley, wheel and axle • The Inclined Plane Family : inclined plane, wedge, and screw.

  4. Types of Simple Machines Simple Machine – device that does work with only one movement.

  5. Levers are divided into 3 classes • All levers have a rigid arm that turns around a point called a fulcrum. 1st Class 2nd Class 3rd Class

  6. Lever Family : Pulleys are modified Levers • A pulley is like a lever. The point in the middle of a pulley is like the fulcrum of a lever. The rest of the pulley acts like the rigid arm of a first class lever.

  7. Lever Family : Wheel and Axle • A wheel and axle has a larger wheel (or wheels) connected by a smaller cylinder (axle) and is fastened to the wheel so that they turn together. When the axle is turned, the wheel moves a greater distance than the axle, but less force is needed to move it. The axle moves a shorter distance, but it takes greater force to move it. Examples: Door Knob, Wagon, Toy Car

  8. The Inclined Plane Family Inclined Plane • A sloping surface, such as a ramp. An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. Examples: Staircase, Ramp, Ladder

  9. The Inclined Plane Family Wedge • Two inclined planes joined back to back. Wedges are used to split things. Examples: Axe, Zipper, Knife

  10. The Inclined Plane Family • An inclined plane wrapped around a shaft or cylinder. This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated. Screw Examples: Bolt, Spiral Staircase

  11. Compound Machines • Compound machine – a machine made of more than one simple machine.

  12. Section 9.2 Summary • The most basic machines are called simple machines. There are six types of simple machines in two families. • Levers have a rigid arm and a fulcrum. There are three classes of levers. • Pulleys and wheel-and-axle machines are also in the lever family. • The inclined plane family includes inclined planes, wedges, and screws. • Compound machines are made of two or more simple machines.

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