2 Types of Simple Machines A simple machine is a machine that does work with only one movement of the machine.There are six types of simple machines: lever, pulley, wheel and axle, inclined plane, screw and wedge.
3 LeverLevera bar that is free to pivot about a fixed point, or fulcrum“Give me a place to stand and I will move the Earth.”– ArchimedesEngraving from Mechanics Magazine, London, 1824Effort armResistancearmFulcrum
4 Lever Le must be greater than Lr in order to multiply the force. Ideal Mechanical Advantage (IMA)frictionless machineMA greater than 1 increases forceEffort arm lengthResistancearm lengthLe must be greater than Lr in order to multiply the force.
5 Lever First Class Lever can increase force, distance, or neither changes direction of force
7 LeverThird Class Leversalways increases distance
8 Problems Lr Le Lr = 20 cm IMA = Le ÷ Lr Le = 80 cm You use a 100 cm plank to lift a large rock. If the rock is 20 cm from the fulcrum, what is the plank’s IMA?GIVEN:Lr = 20 cmLe = 80 cmIMA = ?WORK:IMA = Le ÷ LrIMA = (80 cm) ÷ (20 cm)IMA = 4IMALeLr20cm100cm
9 PulleyPulleygrooved wheel with a rope or chain running along the groovea “flexible first-class lever”FLeLr
10 Pulley Ideal Mechanical Advantage (IMA) equal to the number of supporting ropesIMA = 0IMA = 1IMA = 2
11 Pulley Fixed Pulley IMA = 1 does not increase force changes direction of force
12 Pulley Block & Tackle combination of fixed & movable pulleys increases force (IMA = 4)may or may not change direction
13 The Block and TackleThe block and tackle shown has a IMA of 4.
14 Pulley Movable Pulley IMA = 2 Multiplies force doesn’t change direction
15 Movable PulleysFor a fixed pulley, the distance you pull the rope downward equals the distance the weight moves upward.For a movable pulley, the distance you pull the rope upward is twice the distance the weight moves upward.
16 Wheel and Axle Wheel and Axle two wheels of different sizes that rotate togethera pair of “rotating levers”WheelAxle
17 Wheel and Axle Ideal Mechanical Advantage (IMA) effort force is usu. applied to wheelaxle moves less distance but with greater forceeffort radiusresistance radius
18 Wheel and AxleDoorknobs, screwdrivers, and faucet handles are examples of wheel and axles.Usually the input force is applied to the wheel, and the output force is exerted by the axle.
19 Mechanical Advantage of the Wheel and Axle A wheel and axle is another modified lever.The center of the axle is the fulcrum.The input force is applied at the rim of the wheel.So the length of the input arm is the radius of the wheel.
20 Inclined Plane Inclined Plane Slanted surface used to raise objects h
21 ScrewScrewinclined plane wrapped in a spiral around a cylinder
22 The Screw The IMA of a screw is related to the spacing of the threads. The IMA is larger if the threads are closer together. However, if the IMA is larger, more turns of the screw are needed to drive it into some material.
23 WedgeWedgea moving inclined plane with 1 or 2 sloping sides
25 Compound MachinesTwo or more simple machines that operate together form a compound machine.A car is a compound machine.Burning fuel in the cylinders of the engine causes the pistons to move up and down.
26 Compound MachinesThis up-and-down motion makes the crankshaft rotate.
27 Compound MachinesThe force exerted by the rotating crankshaft is transmitted to the wheels through other parts of the car, such as the transmission and the differential.Both of these parts contain gears, that can change the rate at which the wheels rotate, the force exerted by the wheels, and even reverse the direction of rotation.