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Cultivating tools and harvesting machines were seen by Robert Wade as two of the greatest needs of farmers at the time. John reportedly invented a turnip-drill, a potato-washer, and a straw-elevator for a thresher, but he appears to have patented only one machine, a post-hole auger, and that in conjunction with John Helm of Port Hope, one of the province’s first manufacturers of reapers.
A simple machine is a mechanical device that changes the direction or magnitude of a force. [1] In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. [2] Usually the term refers to the six classical simple machines that were defined by Renaissance scientists: [3] [4 ...
- Overview
- The inclined plane
- The lever
- The wedge
- The wheel and axle
simple machine, any of several devices with few or no moving parts that are used to modify motion and the magnitude of a force in order to perform work. They are the simplest mechanisms known that can use leverage (or mechanical advantage) to increase force. The simple machines are the inclined plane, lever, wedge, wheel and axle, pulley, and screw...
An inclined plane consists of a sloping surface; it is used for raising heavy bodies. The plane offers a mechanical advantage in that the force required to move an object up the incline is less than the weight being raised (discounting friction). The steeper the slope, or incline, the more nearly the required force approaches the actual weight. Expressed mathematically, the force F required to move a block D up an inclined plane without friction is equal to its weight W times the sine of the angle the inclined plane makes with the horizontal (θ). The equation is F = W sin θ.
The principle of the inclined plane is used widely—for example, in ramps and switchback roads, where a small force acting for a distance along a slope can do a large amount of work.
A lever is a bar or board that rests on a support called a fulcrum. A downward force exerted on one end of the lever can be transferred and increased in an upward direction at the other end, allowing a small force to lift a heavy weight.
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Machinery and Manufacturing
All early people used the lever in some form, for example, for moving heavy stones or as digging sticks for land cultivation. The principle of the lever was used in the swape, or shadoof, a long lever pivoted near one end with a platform or water container hanging from the short arm and counterweights attached to the long arm. A man could lift several times his own weight by pulling down on the long arm. This device is said to have been used in Egypt and India for raising water and lifting soldiers over battlements as early as 1500 bce.
A wedge is an object that tapers to a thin edge. Pushing the wedge in one direction creates a force in a sideways direction. It is usually made of metal or wood and is used for splitting, lifting, or tightening, as in securing a hammer head onto its handle.
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The wedge was used in prehistoric times to split logs and rocks; an ax is also a wedge, as are the teeth on a saw. In terms of its mechanical function, the screw may be thought of as a wedge wrapped around a cylinder.
A wheel and axle is made up of a circular frame (the wheel) that revolves on a shaft or rod (the axle). In its earliest form it was probably used for raising weights or water buckets from wells.
Its principle of operation is best explained by way of a device with a large gear and a small gear attached to the same shaft. The tendency of a force, F, applied at the radius R on the large gear to turn the shaft is sufficient to overcome the larger force W at the radius r on the small gear. The force amplification, or mechanical advantage, is equal to the ratio of the two forces (W:F) and also equal to the ratio of the radii of the two gears (R:r).
If the large and small gears are replaced with large- and small-diameter drums that are wrapped with ropes, the wheel and axle becomes capable of raising weights. The weight being lifted is attached to the rope on the small drum, and the operator pulls the rope on the large drum. In this arrangement the mechanical advantage is the radius of the large drum divided by the radius of the small drum. An increase in the mechanical advantage can be obtained by using a small drum with two radii, r1 and r2, and a pulley block. When a force is applied to the large drum, the rope on the small drum winds onto D and off of d.
A measure of the force amplification available with the pulley-and-rope system is the velocity ratio, or the ratio of the velocity at which the force is applied to the rope (VF) to the velocity at which the weight is raised (VW). This ratio is equal to twice the radius of the large drum divided by the difference in the radii of the smaller drums D and d. Expressed mathematically, the equation is VF/VW = 2R/(r2 - r1). The actual mechanical advantage W/F is less than this velocity ratio, depending on friction. A very large mechanical advantage may be obtained with this arrangement by making the two smaller drums D and d of nearly equal radius.
- The Editors of Encyclopaedia Britannica
The simple machines are: inclined plane. wheel and axle. pulley. lever. wedge. screw. Each of these simple machines allows work to be performed with less effort, by trading off effort (applied force) for distance. Recall that work is the product of force and distance: W = Fx W = F x, so that the same amount of work W W may be accomplished by ...
Solution. This is an example of using the formulation of conservation of mechanical energy for simple machines that we introduced in this section: (Fd)in = (Fd)out (F d) in = (F d) out. We can start by listing known values and determining other values which are part of this equation from the given information. (d)out = 0.25 m (d) out = 0.25 m.
Aug 16, 2024 · Summary. Simple machines are devices with few or no moving parts that make work easier. Students are introduced to the six types of simple machines — the wedge, wheel and axle, lever, inclined plane, screw, and pulley — in the context of the construction of a pyramid, gaining high-level insights into tools that have been used since ancient ...
Feb 1, 2022 · Lever. Inclined plane. Pulley. Screw. Wedge. Additional resources. Bibliography. Throughout history, humans have developed several simple machines to make work easier. The most notable of these ...
