Answer: The velocity of the particle is -2 m/s
Step-by-step explanation:
Velocity is defined as the ratio of displacement of a particle to the time taken by the particle. The units of velocity is meters per second.
The equation representing velocity of a particle is given as:

From the graph:
The particle has traveled a distance of 12 m in the downward direction in between 6 to 12 seconds.
Displacement of particle = -12 m
Time taken = 12 - 6 = 6 sec
Putting values in above equation, we get:

Negative side represents the particle is moving in downward direction.
Hence, the velocity of the particle is -2 m/s