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Schoolchildren in the US performing jumping jacks. A jumping jack, also known as a star jump and called a side-straddle hop in the US military, is a physical jumping exercise performed by jumping to a position with the legs spread wide and the hands going overhead, sometimes in a clap, and then returning to a position with the feet together and the arms at the sides.
Pressure in water and air. Pascal's law applies for fluids. Pascal's principle is defined as: A change in pressure at any point in an enclosed incompressible fluid at rest is transmitted equally and undiminished to all points in all directions throughout the fluid, and the force due to the pressure acts at right angles to the enclosing walls.
Real talk: The thought of doing jumping jacks may be only slightly more enticing than burpees. It may bring back memories of pre-dodgeball warm-ups back when dodgeball was part of gym class. Yet ...
Newton's cradle is a device, usually made of metal, that demonstrates the principles of conservation of momentum and conservation of energy in physics with swinging spheres. When one sphere at the end is lifted and released, it strikes the stationary spheres, compressing them and thereby transmitting a pressure wave through the stationary ...
A 2.5-ton house jack that stands 24 inches from top to bottom fully threaded out. A house jack, also called a screw jack, is a mechanical device primarily used to lift buildings from their foundations for repairs or relocation. A series of jacks is used and then wood cribbing temporarily supports the structure. This process is repeated until ...
In a jump from stationary (i.e., a standing jump), all of the work required to accelerate the body through launch is done in a single movement. In a moving jump or running jump, the jumper introduces additional vertical velocity at launch while conserving as much horizontal momentum as possible. Unlike stationary jumps, in which the jumper's ...
One in the lower pulled the crane down the road and ran a hydraulic pump for the outriggers and jacks. The one in the upper ran the upper through a hydraulic pump of its own. Many older operators favor the two-engine system due to leaking seals in the turntable of aging newer design cranes.
A jumping jack toy, c.1850. The jumping jack is a jointed, flat wooden figure, a cross between a puppet and a paper doll that is considered a mechanical toy. The figure's joints are connected to a pull string that causes the arms and legs to move up and down when the string is pulled and released. Jumping jacks were popular in many contemporary ...