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In kinematics, the speed (commonly referred to as v) of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity. [ 1] The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of ...
To state this formally, in general an equation of motion M is a function of the position r of the object, its velocity (the first time derivative of r, v = dr dt ), and its acceleration (the second derivative of r, a = d2r dt2 ), and time t. Euclidean vectors in 3D are denoted throughout in bold.
The general formula for the escape velocity of an object at a distance r from the center of a planet with mass M is [12] = =, where G is the gravitational constant and g is the gravitational acceleration. The escape velocity from Earth's surface is about 11 200 m/s, and is irrespective of the direction of the object.
The comoving distance from an observer to a distant object (e.g. galaxy) can be computed by the following formula (derived using the Friedmann–Lemaître–Robertson–Walker metric): = ′ (′) where a(t′) is the scale factor, t e is the time of emission of the photons detected by the observer, t is the present time, and c is the speed of ...
Proper motion may alternatively be defined by the angular changes per year in the star's right ascension ( μα) and declination ( μδ) with respect to a constant epoch . The components of proper motion by convention are arrived at as follows. Suppose an object moves from coordinates (α 1, δ 1) to coordinates (α 2, δ 2) in a time Δ t.
A Dead Reckoning, DR, is calculated by using a previously determined position on a chart, and advancing that position based on known or estimated speed over a set amount of time. This can be calculated by using the formula Speed = Distance / Time. [3] Once an advance position has been plotted, then set and drift can be factored in.
Special relativity. Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events, as measured by observers situated at varying distances from a gravitating mass. The lower the gravitational potential (the closer the clock is to the source of gravitation), the slower time passes, speeding up as ...
Relative velocities between two particles in classical mechanics. The figure shows two objects A and B moving at constant velocity. The equations of motion are: = +, = +, where the subscript i refers to the initial displacement (at time t equal to zero).