Velocity

• Rate of change of position i.e. rate of displacement with time is called velocity.

• Velocity can be positive, negative or zero. But speed can be positive or zero but it cannot be negative.

[Where 'S' is the distance covered and 't' is the time taken]

SI unit of velocity is m/s (meter/second).

[∵ SI unit of distance is meter and that of time is second]

Velocity is a vector quantity.

Note:

• Velocity is defined as the distance travelled in a specified direction in unit time. The distance in a specified direction is displacement. Therefore, velocity can be defined as the rate of change of displacement.

Uniform velocity:

• A particle is said to have uniform velocity, if magnitudes as well as direction of its velocity remains same and this is possible only when the particles moves in same straight line without reversing its direction. The velocity of a particle is said to be uniform if it covers equal displacement in equal intervals of time, however small the intervals may be.

Non-uniform velocity:

• A particle is said to have non-uniform velocity, if either of magnitude or direction of velocity changes (or both changes).

Average velocity:

• The average velocity of a particle is defined as the ratio of its total displacement to the total time interval during which the displacement occurs.

x(t) and x(t’) is the position at time t and t’.

x(t’) – x(t) is the displacement in the time interval t’ – t.

• Suppose a body travels with a velocity v₁ for t₁ and velocity v₂ for t₂ then the average velocity
• It is defined as the ratio of displacement to time taken by the body