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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 the ...
Velocity is a physical vector quantity: both magnitude and direction are needed to define it. The scalar absolute value ( magnitude) of velocity is called speed, being a coherent derived unit whose quantity is measured in the SI ( metric system) as metres per second (m/s or m⋅s −1 ). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. If there is ...
Terminal velocity is the maximum speed attainable by an object as it falls through a fluid ( air is the most common example). It is reached when the sum of the drag force ( Fd) and the buoyancy is equal to the downward force of gravity ( FG) acting on the object. Since the net force on the object is zero, the object has zero acceleration.
For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c/1.5≈ 200000 km/s (124000 mi/s); the refractive index of airfor visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
Scalar (physics) In physics, scalars (or scalar quantities) are physical quantities that are unaffected by changes to a vector space basis (i.e., a coordinate system transformation). Scalars are often accompanied by units of measurement, as in "10 cm ". Examples of scalar quantities are mass, distance, charge, volume, time, speed, and the ...
Acceleration is the rate of change of velocity. At any point on a trajectory, the magnitude of the acceleration is given by the rate of change of velocity in both magnitude and direction at that point. The true acceleration at time t is found in the limit as time interval Δt → 0 of Δv/Δt.
In physics, circular motion is a movement of an object along the circumference of a circle or rotation along a circular arc. It can be uniform, with a constant rate of rotation and constant tangential speed, or non-uniform with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves the circular motion ...
Kinetic energy may be best understood by examples that demonstrate how it is transformed to and from other forms of energy. For example, a cyclist uses chemical energy provided by food to accelerate a bicycle to a chosen speed. On a level surface, this speed can be maintained without further work, except to overcome air resistance and friction.