Answer:
[tex]a=36\: \sf ms^{-2}[/tex]
Step-by-step explanation:
[tex]\textsf{Displacement}\:x=4t^3-27t+8[/tex]
[tex]\implies \textsf{Velocity}\:v=\dfrac{dx}{dt}=12t^2-27[/tex]
[tex]\implies \textsf{Acceleration}\:a=\dfrac{dv}{dt}=24t[/tex]
At the moment the direction of motion of P reverses, the velocity of P will be zero. Therefore, find the value of t when v = 0:
[tex]\implies v=0[/tex]
[tex]\implies 12t^2-27=0[/tex]
[tex]\implies t^2=\dfrac{27}{12}=\dfrac94[/tex]
[tex]\implies t=\pm\sqrt{\dfrac94}=\pm\dfrac32[/tex]
As time is positive, P reverses when t = 3/2 s
To find acceleration at this time, simply substitute the found value of t into the equation for acceleration:
[tex]\implies a=24(\frac32)[/tex]
[tex]\implies a=36\: \sf ms^{-2}[/tex]
