Julian Calendar

the calendar introduced by Julius Caesar. Based on a year of 365.25 days, it remains the calendar in use today although it is modified.

Taken from Dictionary of Science

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The Julian calendar, a reform of the Roman calendar, was introduced by Julius Caesar in 46 BC, and came into force in 45 BC (709 ab urbe condita). It was chosen after consultation with the astronomer Sosigenes of Alexandria and was probably designed to approximate the tropical year, known at least since Hipparchus. It has a regular year of 365 days divided into 12 months, and a leap day is added to February every four years. Hence the Julian year is on average 365.25 days long.

The Julian calendar remained in use into the 20th century in some countries as a national calendar, but it has generally been replaced by the Gregorian calendar introduced by Pope Gregory XIII in 1582. It is still used by the Berber people of North Africa, on Mount Athos, and by many national Orthodox churches. Orthodox Churches no longer using the Julian calendar typically use the Revised Julian calendar rather than the Gregorian calendar.

The notation "Old Style" (OS) is sometimes used to indicate a date in the Julian calendar, as opposed to "New Style" (NS), which either represents the Julian date with the start of the year as 1 January or a full mapping onto the Gregorian calendar. This notation is used in reference to dates from tsarist Russia (the country did not switch to the Gregorian calendar until 1918).

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Gale

a wind of force 8 on the BEAUFORT SCALE (more than 30 knots).

Taken from Dictionary of Science

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A gale is a very strong wind. There are conflicting definitions of how strong. The U.S. Government's National Weather Service defines a gale as 34 to 47 knots (63 - 87 km/h or 17.5 - 24.2 m/s or 39 - 54 miles/hour) of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are expected.

Other sources use minimums as low as 28 knots (52 km/h) and maximums as high as 90 knots (170 km/h). Through 1986, the National Hurricane Center used the term gale to refer to winds of tropical storm force for coastal areas, between 33 knots (61 km/h) and 63 knots (117 km/h). The 90-knot (170 km/h) definition is very non-standard. A common alternative definition of the maximum is 55 knots (102 km/h).

The most common way of measuring winds is with the Beaufort scale (pronounced /ˈboʊfət/). It is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort wind force scale.

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Young's Modulus

Young's modulus (E) relates the STRESS and STRAIN in a solid (usually wire) using the following formula:

E = stress/strain = σ/ε

where σ = Force/Area and E = Change in Length/Length

Young's modulus has units of newtons per metre squared (Nm^-2) and is calculated only when the material is under elastic conditions, i.e., the force applied does not exceed the elastic limit and cause deformation.

Taken from Dictionary of Science

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In solid mechanics, Young's modulus (E) is a measure of the stiffness of an isotropic elastic material. It is also known as the Young modulus, modulus of elasticity, elastic modulus (though Young's modulus is actually one of several elastic moduli such as the bulk modulus and the shear modulus) or tensile modulus. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. This can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material.

Young's modulus is named after Thomas Young, the 19th century British scientist. However, the concept was developed in 1727 by Leonhard Euler, and the first experiments that used the concept of Young's modulus in its current form were performed by the Italian scientist Giordano Riccati in 1782 — predating Young's work by 25 years.

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Joule

the unit for all ENERGY measurements. It is the mechanical equivalent of heat, and one joule (J) is equal to a force of one NEWTON moving one metre, i.e. 1J = 1Nm. It is named after James Prescott Joule (1818-1889), a British physicist who investigated the relationship between mechanical, electrical and heat energy, and, from such investigations, proposed the first law of THERMODYNAMICS, the conservation of energy.

Taken from Dictionary of Science

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The joule (symbol J), named for James Prescott Joule, is the derived unit of energy in the International System of Units. It is the energy exerted by the force of one newton acting to move an object through a distance of one metre. In terms of dimensions:

One joule is defined as the amount of work done by a force of one newton moving an object through a distance of one metre. Other relationships are:

• The work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt (C·V). This relationship can be used to define the volt;

• The work required to continuously produce one watt of power for one second; or one watt second (W·s) (compare kilowatt hour). This relationship can be used to define the watt.

Taken from Wikipedia

Acceleration

is when the speed at which an object is traveling is further increased. The object travels faster because some force is applied to push or pull the object, making it move more quickly. In physics, when calculations are made concerning acceleration, it is usually represented by the symbol α and is measured in metres per second, per second or metres per second squared (written in mathematical shorthand as ms^-2).

When bodies fall freely under the influence of the force of GRAVITY they all fall at the same rate, that is at a uniform acceleration. Whether the object is a lead weight or a feather they fall at the same rate due to gravity. The reason that in reality the lead weight hits the ground before the feather is due to air resistance holding back the feather. Acceleration due to gravity is approximately 9.8 metres per second per second so when the air resistance is very little, the velocity (speed) of a falling object increases by 9.8 metres per second, per second. On the other hand, an object shot straight upwards with a particular velocity will slow down (decelerate) by the same rate every second until it reaches its greatest height after a particular period of time. When this maximum height is reached, the object that had been shot straight upwards (no horizontal motion whatsoever) will start to fall with an acceleration of 9.8 ms-2.

Taken from Dictionary of Science

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In physics, and more specifically kinematics, acceleration is the change in velocity over time. Because velocity is a vector, it can change in two ways: a change in magnitude and/or a change in direction. In one dimension, i.e. a line, acceleration is the rate at which something speeds up or slows down. However, as a vector quantity, acceleration is also the rate at which direction changes. Acceleration has the dimensions L T⁻². In SI units, acceleration is measured in metres per second squared (m/s²).

In common speech, the term acceleration commonly is used for an increase in speed (the magnitude of velocity); a decrease in speed is called deceleration. In physics, a change in the direction of velocity also is an acceleration: for rotary motion, the change in direction of velocity results in centripetal (toward the center) acceleration; where as the rate of change of speed is a tangential acceleration.

In classical mechanics, for a body with constant mass, the acceleration of the body is proportional to the resultant (total) force acting on it (Newton's second law):

where F is the resultant force acting on the body, m is the mass of the body, and a is its acceleration.

Taken from Wikipedia