A jack is a mechanical lifting device used to apply great forces or lift heavy loads. A mechanical jack employs a screw thread for lifting heavy equipment . The hydraulic jack uses hydraulic power .  The most common form is a car jack, floor jack or garage jack, which lifts vehicles so that maintenance can be performed. Jacks are usually rated for maximum lifting capacity (for example, 1.5 tons or 3 tons). Industrial jacks can be rated for several tonnage loads .
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The personal name Jack , which came into English usage around the thirteenth century as a surname for John, was used in the sixteenth century as a colloquial term for ‘a man (of low status)’ (as much as ‘Harfan’ in modern usage). Maula, Harfan incomplete’). From here the term is applied to ‘things which in some way replace a boy or a man, or save human labour’. The first attestation in the Oxford English Dictionary of Jack is from 1679, meaning ‘a machine, usually portable, for lifting heavy weights by acting from below’, ‘an engine used for removing great timber and placing commodius’. ‘ is mentioned.
Scissor car jacks typically use mechanical advantage so that a human can lift the vehicle by manual force alone. The jack shown on the right is designed for a modern vehicle and the notch fits into the jack-up point  on a unibody . Earlier versions contained a platform for lifting on the vehicle’s frame or axle.
Electrically operated car scissor jacks are powered by 12 volt electricity supplied directly from the car’s cigarette lighter receptacle . Electrical energy is used to automatically raise and lower these car jacks. Electric jacks require less effort from the motorist for operation.
A house jack, also called a screw jack, is a mechanical device primarily used to lift buildings from their foundations for repair or relocation . A series of jacks are used and then a wooden cradle temporarily supports the structure. This process is repeated until the desired height is reached. House jacks can be used for jacking -carrying beams that have been settled or can be used to install new structural beams . At the top of the jack is a cast iron circular pad on which the jacking post rests. This pad house moves independently of the jack so it won’t bend because acme-threadedThe rod is rotated by a metal rod. This piece bends quite a bit, but not enough to make the post dangerously out of plumb .
In 1838 William Joseph Curtis filed a British patent for a hydraulic jack. 
In 1851, inventor Richard Dudgeon was granted a patent for a “portable hydraulic press “—the hydraulic jack, a jack that proved to be far superior to the screw jacks in use at the time.
Hydraulic jacks are generally used for shop work, not as an emergency jack with a vehicle. The use of a jack not designed for a specific vehicle requires more than usual care in selecting ground conditions, the jacking point on the vehicle, and ensuring stability when the jack is extended. Hydraulic jacks are often used to lift elevators in low and medium buildings.
A hydraulic jack uses a liquid, which is incompressible, to be forced into a cylinder by a pump plunger. Oil is used because it is self lubricating and stable. When the plunger pulls back, it removes oil from the reservoir through a suction check valve in the pump chamber. When the plunger moves forward, it pushes the oil into the cylinder through the discharge check valve. The suction valve is within the ball chamber and opens with each draw of the plunger. The discharge valve is outside the ball chamber and opens when oil is pushed into the cylinder. At this point the suction ball within the chamber is forcibly closed and oil pressure builds up in the cylinder.
A floor jack (aka ‘trolley jack’) consists of a horizontal piston pushed onto the short end of a bellcrank , with the longer arm providing vertical movement to a lifting pad, which is held horizontal with a horizontal linkage. Floor jacks typically include casters and wheels, which allow compensation for the arc taken by the lifting pad. This mechanism provides a low profile, allowing for considerable extension, for easy maneuvering under the vehicle.
A bottle jack or whiskey jack  is a jack that resembles a bottle in shape, with a cylindrical body and a neck. Inside is a vertical lifting ram with some kind of support pad fixed on top. The jack may be hydraulic or work by screw action. In the hydraulic version, the hydraulic ramEither at the baseplate or via a pressure hose at a remote location the body is discharged vertically by hydraulic pressure provided by a pump. With single action pistons the lift range is somewhat limited, so its use for lifting vehicles is limited to those with relatively high clearance. For lifting structures such as homes the hydraulic interconnection of multiple vertical jacks via valves enables uniform distribution of forces while enabling close control of the lift.
The screw version of the bottle jack works by turning a large nut running on a vertical ram threaded into the neck of the body. The nut has gear teeth, and is usually rotated by a bevel gear attached to the body, the bevel gear is rotated manually by a jack handle fitting into a square socket. There may be a second screw ram inside the ram, which doubles the lifting range from the telescopic. Bottle jacks have a capacity of up to 50 tons and can be used to lift a variety of items. Typical uses include automobile and home foundation repair. Larger, heavier-duty models may be referred to as a barrel jack. This type of jack is best used for small vertical lifts.  Blocks can be used to repeat operations when a greater amount of height is needed. 
Air hydraulic jack
An air hydraulic jack is a hydraulic jack that is driven by compressed air—for example, air from a compressor —rather than human work. This eliminates the need for the user to activate the hydraulic mechanism, saving effort and potentially increasing speed. Sometimes, such jacks can also be operated by the normal hydraulic actuation method, thereby retaining functionality even when a source of compressed air is not available.
An inflatable jack, lifting bag, or pneumatic lifting bag is an air bag that is inflated with compressed air (without a hydraulic component) to lift objects. The bag can be deflated to be reused later. The objects may be of a small weight such as an automobile  or it may be of a larger object such as an airplane. [11 1]
Air bags are also used by rescue teams to lift heavy objects to aid victims trapped under those objects. There are three main types of lifting bags to the rescue: high pressure, medium pressure and low pressure systems. Low pressure bags operate at 7.25 psi for high vertical lift at low lifting capacity over a large surface area. Medium pressure bags operate at 15 psi. High-pressure bags that have a higher lifting capacity operate at pressures between 90 and 145 psi. Two air bags can be stacked together to provide a higher lift. It is recommended that no more than two bags can be used in a stacked configuration, the larger bag should be the bottom one, And no other objects should be inserted between the stacked bags. Incorrect use of a stacked bag can result in the bag (or other objects) popping out to form a dangerous projectile.
A strand jack is a special hydraulic jack that grabs steel cables. Often used in concert, strand jacks can lift hundreds of tons and are used in engineering and construction.
Farm jacks, also known as railroad jacks, high lift jacks or kanga-jacks, were invented in 1905. It consists of a steel beam with equally spaced holes along its length, and a hand-operated mechanism that can be moved. Through the use of a pair of climbing pins from one end of the beam to the other. Typical sizes for farm jacks in terms of beam length are 4 feet (1.2 m), 5 feet (1.5 m) and 6 feet (1.8 m).
The versatility of the jack stems from its use for such applications as lifting, winching, clamping, pulling and pushing. It is this versatility, as well as long travel and its relative portability, that make the Farm Jack so popular with off-road drivers.
National and international standards have been developed to standardize safety and performance requirements for jacks and other lifting equipment. The selection of the standard is an agreement between the purchaser and the manufacturer, and has some significance in the design of the jack. In the United States, ASME has developed a safety standard for portable automotive service equipment, which was last revised in 2014, which includes hydraulic hand jacks, transmission jacks, emergency tire change jacks, service jacks, fork lift jacks and Other lifting equipment requirements are included.