What causes variation in velocity of a particle ?

What is variation?

The velocity of a particle is zero at t=0

A particle moves along the x-axis in such a way that its coordinates x varies with time 't' according to the equation x=2-5t+6t^(2) . What is the initial velocity of the particle?

The position of a particle is given by r=2.00t hati-1.00t^(2)hatj+3.00hatk where t is in seconds and the coefficients have the proper unit for r to be in metres. Find the velocity and acceleration of a particle then what is the magnitude and direction of velocity of the particle at t = 2 s?

The product of mass and velocity of a particle is

What causes plaque ?

What causes hardness in water ?

A particle moves in a region having a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be