As the particle moves along a straight line, the magnitude of the velocity is equal to the speed and the direction is along the direction of motion.
To find out the speed of the particle, we have to differentiate the given equation of motion. That is,
Speed = [tex] \frac{d(s)}{dt} \\ =\frac{d(100+60t-4.5t^{2})}{dt} \\ =0+60-9t [/tex]
For t=6 s, we get
Speed = 60₋ 9 × 6 = 60₋54=6 m/s
The speed of the particle at t=6 s is 6 m/s.
