A continuous change in the position of the object with respect to time is called motion.
Rectilinear motion: If an object moving in a straight line changes its position with respect to time.
Circular motion: When an object moves at a constant distance from a fixed point, its motion is called circular motion.
Periodic motion: A motion which repeats itself after certain fixed interval of time is called periodic motion.
Oscillatory motion: A motion which is repeated about its mean position periodically is called oscillatory motion. For example, motion of simple pendulum.
Distance: The length of the path fallowed by a body is called distance.
Displacement: The shortest distance between initial and final position of the object is called displacement. It is vector quantity.
The SI unit of distance and displacement is metre (m).
Speed: Distance traveled by a body in unit time is called speed.
Speed = Distance / Time
Average speed: Total distance traveled / Total time taken
Velocity: Displacement of a body in unit time is called velocity.
Velocity = Displacement / Time taken
The unit of velocity in SI system is m/s. Other commonly used unit is km/h. It is a vector quantity.
Acceleration: The rate of change of velocity is called acceleration.
Acceleration = (Final velocity – initial velocity) / Time
a = (v - u)/t
The unit of acceleration in SI unit is ms-2. It is a vector quantity.
Equations for uniformly accelerated motion:
- v = u + at
- s = ut + ½at2
- v2 = u2 + 2as
where u = initial velocity, v = final velocity, a = acceleration, s = distance, t = time