![]() ![]() These are everyday applications of this mechanism.Ī compound lever translates the small movement of a piano key to the fast, hard strike of the hammer on the stringsĪ piano key is a compound lever of the first-class, since the fulcrum is between the weight to be moved and the power. The train brake translates the force of pushing back the stick to the levers and they rub against the wheels, using friction to slow and eventually stop the train. These all use multiple levers to magnify force to accomplish a specific purpose. Compound balances are used to weigh heavy items. Another example is the elbow-joint press, which is used in printing, molding or handloading bullets, minting coins and medals, and in hole punching. Note that (7 + 1) cm = 8 cm is the distance from the point of application of the effort to the fulcrum of the first lever, perpendicular to the applied effort.Įxamples A handloading press uses a compound lever to reduce the force the operator must apply and confine the action to a relatively small space.Ī few examples of the compound lever are the scale, train brakes, and a common type of nail clippers. In this example, W/F is 7 + 1 / 1 × 6 / 6 + 2 = 6. In the example of a nail clipper on the right (a compound lever made of a class 2 and a class 3 lever), because the effort is applied vertically (that is, not perpendicular to the lever), distances to the respective fulcrums are measured horizontally, instead of along the lever. ![]() The distances used in calculation of mechanical advantage are measured perpendicular to the force. This is not usually the goal of a compound lever system, though in rare situations the geometry may suit a specific purpose.Ĭalculation of the mechanical advantage of a nail clipper With the dimensions shown, the mechanical advantage, W/F can be calculated as 10 / 3 × 9 / 4 = 7.5, meaning that an applied force of 1 pound (or 1 kg) could lift a weight of 7.5 lb (or 7.5 kg).Īlternatively, if the position of the fulcrum on lever AA' were moved so that A1 = 4 units and A2 = 9 units, then the mechanical advantage W/F is calculated as 4 / 9 × 9 / 4 = 1, meaning that an applied force will lift an equivalent weight and there is no mechanical advantage. The figure on the left illustrates a compound lever formed from two first-class levers, along with a short derivation of how to compute the mechanical advantage. The output from one lever becomes the input for the next lever in the system, and so the advantage is magnified. In all types of compound lever, the rule is that force multiplied by the force arm equals the weight multiplied by the weight arm. Compound levers can be constructed from first, second and/or third-order levers. In these conditions, combinations of simple levers, called compound levers, are used. In practice, conditions may prevent the use of a single lever to accomplish the desired result, e.g., a restricted space, the inconvenient location of the point of delivery of the resultant force, or the prohibitive length of the lever arm needed. Calculation of the mechanical advantage of a compound lever made of two class 1 leversĪ lever arm uses the fulcrum to lift the load using and intensifying an applied force.
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