At time t=0,the current to the DC motor is reversed resulting in angular displacement of the motor shaft given by (angle =(198rad/s))t-(24rad/s^2)t^2-(2rad/s^3/)t^3 a) at what time is the angular velocity of the motor shaft zero?

1 Answer
Apr 12, 2018

The time is #=3s#

Explanation:

The angle is

#theta=198t-24t^2-2t^3#

The angular velocity is

#omega=(d theta)/(dt)#

#=198-48t-6t^2#

Therefore,

#omega=0#

when

#198-48t-6t^2=0#

#<=>#, #t^2+8t-33=0#

#<=>#, #(t+11)(t-3)=0#

Therefore,

#t=-11# or #t=3#

Discard the negative value

The time is #=3s#