That a terrible quarrel broke out among the Supreme Polemarch in the Achaean army...
To characterize motion, the concept of average speed is introduced: In physics, the greatest interest is not the average, but instantaneous speed, which is defined as the limit to which the average speed tends over an infinitesimal period of time Δt: In mathematics, such a limit is called the derivative and is denoted or
AVERAGE SPEED is a vector physical quantity equal to the ratio of the movement made by the body during time t to this time. AVERAGE GROUND SPEED is a scalar physical quantity equal to the ratio of the path traveled by a body in time t to this time. INSTANTANEOUS SPEED () is a vector physical quantity equal to the ratio of the movement made by a particle in a very short period of time to this period of time. By a very small (or, as they say, physically infinitesimal) period of time is meant here one during which the movement can be considered uniform and rectilinear with sufficient accuracy. At each moment of time, the instantaneous velocity is directed tangentially to the trajectory along which the particle is moving. Its SI unit is meter per second (m/s).
The instantaneous velocity of a body at any point on a curvilinear trajectory is directed tangentially to the trajectory at that point. The difference between average and instantaneous speeds is shown in Fig. Average and instantaneous speeds, displacements over time, respectively. At t 0
When a body moves along a curved path, its speed changes in magnitude and direction. The change in the velocity vector over a certain short period of time Δt can be specified using a vector. The vector of changes in speed over a short time Δt can be decomposed into two components: one directed along the vector (tangential component) and one directed perpendicular to the vector (normal component)
THE LAW OF ADDITION OF SPEEDS in Newton's classical mechanics is a relationship that connects the speeds of motion of the same particle in two different inertial reference systems. The classical law of addition of velocities: the speed of a particle in a stationary frame of reference is the vector sum of the speed of a body in a moving frame of reference and the speed of the moving frame of reference relative to the stationary frame. It is performed at speeds of bodies and reference systems much lower than the speed of light.
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Slide captions:
Relative speed
1) B different systems reference bodies move differently!
What's relative? Body position is relative! Am I at peace?! Body motion is relative!
Body movement from different perspectives
Classical law of addition of velocities The speed of a body relative to a fixed frame of reference is equal to the geometric sum of the speed of the body relative to a moving system and the speed of a moving system relative to a stationary one
Relative velocity Let us assume that the velocity of two material points is defined in the same frame of reference.
Relative speed is the speed of one material point in a reference system associated with another. If bodies move translationally, the relative speed is equal to the difference in the speeds of these bodies:
Relative speed when moving in one direction When bodies move in one direction, the relative speed module is equal to the speed difference
Relative speed in oncoming traffic In oncoming traffic, bodies approach each other with a relative speed equal to the sum of their speeds, which is why oncoming collisions of cars and trains are so dangerous.
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"Fundamentals of Optics" - Images of a point. Image of point S in a lens. Perpendicular to the mirror. Flat mirror. Camera. Spherical mirrors. Beam. Lenses. Photographic film or photographic plate. Refractive indices. We have derived the lens formula. An object between the focus and the mirror. Experimental laws. An object at a finite distance. Focusing. A ray falls on the mirror at point N. Laws of reflection. Quantities. Reasoning and construction.
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