Motion

Definition
Motion can be defined as the change of position of an object with respect to time. Moving vehicle, Walking person depicts motion. Motion described in terms of displacement, distance, velocity, acceleration.

Types of Motion

 * Linear Motion - Motion is linear when all the parts of an object move from one place to another at a particular time.Ex: Train moving on a track. Linear Motion is further classified as

Rectilinear Motion - When an object in linear motion moves in a straight linear path. Ex: Fig 1.Train moving on a straight track.Curvilinear Motion - When an object in linear motion moves along a curved path. Ex: Fig 2. Train moving a curved track


 * Rotary Motion - Motion is rotary when different particles of an object move in a circular path and travel different distances at any specific time intervals. Here the object rotates on its axis. Ex: Fig 3. A rotating ceiling fan




 * Oscillatory Motion - Motion is Oscillatory when an object oscillates around its mean position. Object repeats the cycle of motion around its mean position. The movement of an object is called Oscillations. Ex: Fig 4. Motion of a pendulum of wall clock

Terminology
Displacement - Displacement is defined as the change in position of an object. Displacement is a vector quantity having direction and magnitude represented as an arrow that points from the starting point to the final position. The standard unit of displacement in the International System of Units (SI) is the meter (m).

Speed - Speed is defined as the distance covered by an object in unit time and measured as the ratio of distance to the time in which the distance was covered. Speed is a scalar quantity as it has only direction and no magnitude. Speed gives us an idea of how fast an object is moving. The standard unit of Speed in the International System of Units (SI) is the meter per second (m/s).

$$Speed = \frac{Distance \ travelled (in \ meters)}{Time\ taken (in \ sec)} $$

Velocity - Velocity is defined as the displacement of the object in unit time. Velocity is a vector quantity as it has both direction and magnitude. Velocity tells us its speed and the direction the body is moving in. The standard unit of Velocity in the International System of Units (SI) is the meter per second (m/s).

Initial Velocity (u) - Initial velocity is the velocity at which the motion starts and is represented by u.

Final Velocity (v)- Final velocity is a vector quantity that measures the speed and direction of a moving body after it has reached its maximum acceleration. It is represented by v.

$$v = u +at $$

Acceleration (a) - Acceleration is the rate of change of velocity with respect to time. The change in the velocity of an object could be an increase or decrease in speed or a change in the direction of motion. A few examples of acceleration are the falling of an apple, when a car is stopped at the traffic lights. Acceleration is a vector quantity as it has both magnitude and direction. This is represented by a.

$$Acceleration \ (in \ meters/sec^2) = \frac{(Final \ velocity - Initial \ velocity ) (in\ meters/sec)}{Time \ ( in \ sec) } $$

$$Acceleration \ (in \ meters/sec^2) = \frac{Change\ in\ velocity \ (in \ meters/sec) }{Time\ (in \ secs) } $$