Elementary Mechanics, Physics tutorial


To begin in physics, the first concept is space, the domain in which objects like bricks, ball bearings, cannonballs, bowling balls, billiard balls, bullets, bombs, anvils, spacecraft, cars, trucks, toys, amusement park rides, planets, rockets and the other natural props of physics examples -- exist and work.

In physics, space is usually stated in Cartesian coordinates, a framework set up to compute location of the object along X, Y, and Z coordinates. Point where the coordinate axes come together, origin, is usually stated to be suitable to problem at hand. In metric system, spatial dimensions are usually described in meters, although for extremely large distances light-years are frequently utilized instead. Space can be thought of as three-dimensional game board in which physical procedures are performed.

Let us consider a scientist named Dexter. If Dexter is in the building, his location could be stated using first-floor entrance as the origin. He could be 19 meters beyond entrance, 11 meters to left of entrance, and (assuming the building has numerous floors), 28 meters above entrance. Dexter's location could then be provided as:

   (X, Y, Z)  = (19, 11, 28)

This triplet of numbers states the three-dimensional vector defining Dexter's location. This vector could be thought of as the arrow which points straight from entrance of building to the location. Vector has a direction and length (or magnitude). This is on the contrary with more familiar scalar, or undirected, quantities, like temperature, which only have magnitude. In the building example, magnitude is a straight-line distance from entrance to Dexter's location. Magnitude can be provided by Pythagorean Theorem as:

   SQRT( X^2  + Y^2  + Z^2 )  =  SQRT( 19^2 + 11^2 + 28^2)  =  35.6 meters

For several simple physics problems, it is only essential to explain them in two dimensions, as XY coordinates. For the common instance, for practical purposes balls on the pool table only move in two dimensions. Such a system is at times called planar. In the case of scientist in a building, if building had only one floor, then Dexter could be positioned just with XY coordinates:

   (X, Y)  = (19, 11)

This is still a vector, with the direction in plane and a magnitude, which by Pythagorean theorem is:

  SQRT( X^2 + Y^2 )  =  SQRT( 19^2 + 11^2 )  =  22.0 meters

Displacement, velocity, and acceleration:

The concept of location in the coordinate system is directly related to another concept in physics, called as displacement. This is just a vector which describes change in location of the moving object. It does not say anything about how it got from place to place or how fast it did it, it simply provides the difference in location.

The movement of objects is called as velocity, or displacement per time. By the way, velocity is not closely the same thing as speed. Velocity is the vector quantity: it is speed in the specific direction. Speed is the scalar quantity, utilized when direction is not significant. Changes in that movement are called as acceleration, or changes in velocity per time; acceleration is also vector quantity.

In standard metric units, velocity is stated in terms of meters per second, whereas acceleration is given in meters per second squared. For instance, if Dexter steps out door of laboratory onto the lawn and drops a brick, it of course accelerates downward in grass at the increasing velocity, because of the force of gravity on brick.

The object falling to the ground on the Earth accelerates at the constant rate of 9.81 meters per second. In mathematical terms:

Acceleration = 9.81

As acceleration is the change in velocity per time, then the velocity is just the acceleration times number of seconds:

 Velocity = acceleration * time = 9.81 * time.

Rest and motion:

To understand the concept of frame of reference it is essential to know certain observations which have been made by physicists about physical world we are living in. One of such observations is that body is said to be at rest when it doesn't change its position with time. It is said to be in motion when it changes its position with time. But if position of the object changes with time or not, we need the point completely fixed in space to be known. Such a fixed or stationary point is not known to exist in universe. Due to this physicists have observed that everything in universe is in constant motion comprising the earth we are living in. Earth revolves round sun and at the same time rotates round polar axis.

Concept of Time:

The complete day comprises of day time and night time segments of earth's rotation. As during day time segment we see sunlight but in the night time segment sunlight is hidden from us and we see only darkness. The sun becomes visible to us to move across sky due to this diurnal rotation of the earth about the polar axis. The meridian at the place is an imaginary vertical plane through it. Sun is said to be in meridian when it reaches the highest position in the course of the evident journey in the sky. The interval of time between two successive transitions of centre of the sun's disc across the meridian at any place is known as a solar day.

Exponential notation and metric prefixes:

It is necessary to understand basic metric units of physical measurement, like joules, meters, watts, and so on. This topic will expand on system of measurements, and to make correct use of it needs the understanding of two things: "exponential notation" and "metric prefixes".

Physics manages quantities which may differ over the wide range, leading to extremely large or very small values, for instance:



In this format, such values are clumsy and working them is error-prone. It is much more suitable to employ exponential notation, with strings of zeroes changed to the power of 10:

1,470,000,000,000 = 1.47 * 1,000,000,000,000

= 1.47 * 10^12

= 1.47E12

0.000000000000592 = 5.92 * 0.000000000001

= 5.92 * 10-12

= 5.92E-12

It should be quite obvious that 10^12 is 10 multiplied by itself 12 times, or 1 followed by 12 zeroes. E12 is a shorthand method of representing this. Likewise, 10^-12 is 1/10 multiplied by itself 12 times, and E-12 is a shorthand format.

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