Introduction to Kinematics,Differences between Distance and Displacement:,Differences between speed and velocity

Kinematics: It is the branch of mechanics that deals with the study of motion of objects is called Kinematics. It doesn’t account for the cause of motion of the body.
Rest: A body is said to be in motion if it doesn’t change its position with time.
Motion: A body is said to be in motion if it changes it position with time in respect to surrounding.

Motion and Rest are relative terms. A body can be at motion with respect to one object and even in motion with respect to another object at the same time.
Some terms regarding motion:
Distance: The actual length of path covered by the body is called distance.
Displacement: The shortest distance covered by the body between two points is called displacement.
Differences between Distance and Displacement:

Remember:

• Distance always increases with time but displacement may increase or decreases with time.
• Displacement and distance have same unit.
• Displacement can never be greater than the distance.
Speed:
The distance travelled by the body in one second is called speed.
Mathematically,


Speed=Distance travelledTime taken
• Uniform Speed: If a body covers equal distance in equal interval of time, the body is said to be in uniform speed. Example: If a body travels a distance of 20 metres in 1 second, then it travels 40 metres in 2 seconds.
• Average Speed: It is the ratio of total distance travelled to total time taken in travelling a certain distance.
• Instantaneous speed: It is speed of any object at a particular instant of time.
Velocity: The rate of change of displacement with respect to time is called velocity.
Mathematically,

Speed=DisplacementTime taken
• Uniform Velocity: If a body covers equal displacement in equal interval of time. The body is said to be in uniform velocity.
  Example: A uniform body has displacement of 200 metres in one minute 400 metres in two seconds.
• Non-Uniform Velocity: A body is said to have non uniform velocity, if it covers unequal displacement in equal interval of time.
  Example: A body has dispacement of 200 metres in one minute and 300 metres in two minute.
• Instantaneous Velocity: The velocity of a body at a particular instant is called instantaneous velocity. Mathematically,  
  v=limΔt→0ΔsΔt=dsdt
• 
  
Differences between speed and velocity:

Acceleration: The rate of change of velocity is called acceleration.

• Average Acceleration: The average rate of change of velocity is called average acceleration. Mathematically,
  Average acceleration(av)=Final velocity (v2)−Initial velocity(v1)Final time (t2)−Initial time(t1)
• 
  
• Instantaneous acceleration: The acceleration of a body at any instant is called instantaneous acceleration.
  a=limΔt→0ΔvΔt=dvdt