Basic Principles of Kinematics

The students were asked to calculate the maximum height reached by the ball, when it was thrown up at a speed of 6 meters per second. Similarly, a morning walker moves on a semi circular track of radius 35 meters. If he starts at one end of the track and reaches at the other end, they were asked to calculate the distance travelled and also the displacement.

The analysis of motion of bodies is studied broadly in a branch of physics known as mechanics.

Kinematics does deal with the path of moving bodies. The cause of their motion is not studied in kinematics. The motion of a vehicle on a straight road is an example of motion in one dimension. The motion of projectile on the earth’s surface is an example of motion with an uniform acceleration in two dimensions. A cricket ball thrown by a fielder is an example of a projectile.

A particle or an object is said to be in motion if it occupies different positions at different instants of time. Otherwise it is said to be at rest.

A change of position in a particular direction is known as displacement. Distance is defined as the total path travelled by an object in any direction. Displacement on the other hand, is the shortest distance in a particular direction.

If a vehicle travels a distance of 150 kilometers in three hours, its speed is 50 kilometers per hour. Velocity of a vehicle is its speed in any specified direction. Velocity (v) is given by the formula, displacement (s) / time (t). When any body does travel equal distances in equal intervals of time while moving in a straight line, it is said to be moving with uniform velocity.

If ‘u’ is the symbol for initial velocity, t is for time, and ‘v’ is for final velocity, then the average velocity is given by the formula: u+v/2. The distance or the displacement (s) can be calculated by multiplying the average velocity with time (t).

The researchers could also derive equations of motion such as, v= u+at. These equations are meant for the particles moving with uniform acceleration along a straight line.

The objects will be subjected to a constant retardation when they go up and a constant acceleration while falling down. Since this natural phenomenon is due to the gravitational force of the earth, it is known as the acceleration due to gravity (g). For freely falling and uniformly accelerated bodies, the equations of motion do change. For instance, the equation, v= u+at, becomes v= u+gt. When the objects go up, the same equation would be written as, v= u-gt.

Distance and speed are scalar quantities. Displacement and velocity are vector quantities. All the particles, from that of electrons to galaxies are in motion in the universe!.

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