48. A particle moves along a straight line such that its displacement at any time [tex] t [/tex] is given by [tex] s = t^3 - 6t^2 + 3t + 4 [/tex] meters. The displacement when the acceleration is zero is:

1. 3 m
2. -12 m
3. 42 m
4. -6 m



Answer :

To determine the displacement of the particle when its acceleration is zero, we will need to undertake the following steps:

1. Identify displacement function: We are given the displacement function:
[tex]\[ s(t) = t^3 - 6t^2 + 3t + 4 \][/tex]

2. Find the velocity function: Velocity ([tex]\(v\)[/tex]) is the first derivative of displacement with respect to time [tex]\(t\)[/tex]:
[tex]\[ v(t) = \frac{ds}{dt} = \frac{d}{dt} (t^3 - 6t^2 + 3t + 4) \][/tex]
Calculate the derivative:
[tex]\[ v(t) = 3t^2 - 12t + 3 \][/tex]

3. Find the acceleration function: Acceleration ([tex]\(a\)[/tex]) is the derivative of velocity with respect to time [tex]\(t\)[/tex]:
[tex]\[ a(t) = \frac{dv}{dt} = \frac{d}{dt}(3t^2 - 12t + 3) \][/tex]
Calculate the derivative:
[tex]\[ a(t) = 6t - 12 \][/tex]

4. Determine when the acceleration is zero: Set the acceleration function equal to zero and solve for [tex]\(t\)[/tex]:
[tex]\[ 6t - 12 = 0 \][/tex]
[tex]\[ 6t = 12 \][/tex]
[tex]\[ t = 2 \][/tex]

5. Find the displacement when [tex]\(t = 2\)[/tex]: Substitute [tex]\(t = 2\)[/tex] back into the displacement function:
[tex]\[ s(2) = (2)^3 - 6(2)^2 + 3(2) + 4 \][/tex]
Calculate the value:
[tex]\[ s(2) = 8 - 24 + 6 + 4 \][/tex]
[tex]\[ s(2) = 8 - 24 + 10 \][/tex]
[tex]\[ s(2) = -6 \][/tex]

Therefore, the displacement when the acceleration is zero is [tex]\(-6 \, \text{m}\)[/tex].

The correct answer is:
[tex]\[ \boxed{-6 \, \text{m}} \][/tex]