16-­‐11-­‐07 Spring Scales Mechanical Advantage Lab Lesson 14 Part 1 – The Lever The Inclined Plane Your Turn •  For a double work grade, submit: –  Completed Table 5.1, including all calculaKons –  Completed Table 5.2, including all calculaKons –  Responses to quesKons 12-­‐13, 15 •  For quesKon 13, explain why •  QuesKon 15 is asking how the MA of levers can be increased and decreased, and how the MA of inclined planes can be increased and decreased Simple Machines: (2) The Pulley (3) The Wheel and Axle Lesson 15 1 16-­‐11-­‐07 The Pulley The Wheel and Axle A pulley is made of a grooved wheel with a rope or cable looped around it; the pulley is free to spin. The pulley itself can either be fixed or can move. You will see examples of pulleys in flagpoles (fixed) and in gym equipment (fixed and movable). A wheel and axle is made of a shaZ or axle a[ached to a larger disk, called a wheel. You will see examples of wheels and axles in bike pedals, doorknobs, and screwdrivers. The IMA of the Pulley The IMA of the Wheel and Axle Since a fixed pulley only changes the direcKon of a force, its IMA is 1. Moveable pulleys, where one end of the rope is fixed and the pulley/s are allowed to move, spread the weight of the object between the support ropes that exist. The IMA of moveable pulleys is equal to the number of its support ropes. An Example The handle of a garden tap of radius 3.0cm is connected to a shaZ of radius 0.50cm. What is the IMA of the wheel and axle? Depending on whether the input force is applied to the wheel or the axle, the mechanical advantage will be greater than or less than 1, respecKvely. Input force applied to the axle: ra / rw Input applied to the wheel: rw / ra One More Example You want to design a doorknob that has an output force twice that of the input force. If the radius of the doorknob’s axle is 1.85cm, what does the radius of the doorknob’s handle need to be? If you were to actually measure the output force, why wouldn’t it be double the input force? 2 16-­‐11-­‐07 Your Turn •  Take jot notes from pp136-­‐138 (not collected, but know for unit test) 3