If a particle moves according to the equation s = t3 – 6t2 + 9t – 5, how do you find the acceleration when the velocity is 0 (s is in cm).?

1 Answer
May 31, 2016

Take the derivative to find the expression for the velocity of the particle. Take the derivative again to find the expression for the acceleration. Set the velocity expression equal to zero and solve the resulting quadratic for s. Plug this value into the expression for the acceleration. You should get pm 6cm"/"sec^2

Explanation:

s = t^3 – 6t^2 + 9t – 5

v={ds}/{dt} = 3t^2 – 12t + 9

a={dv}/{dt}={d^2s}/{dt^2} = 6t – 12

v= 3t^2 – 12t + 9=0

3(t^2 – 4t + 3)=0

(-1)*(-3)=3 and (-1)+(-3)=-4

so x-3, and x-1 are factors

3(t – 3)(t - 1)=0

we have roots t_1=1 and t_2=3

Plug these into a

a_1 = 6(1) – 12=-6

a_2 = 6(3) – 12=6