The position \(x\) of a particle varies with time \((t)\) as \(x=a t^{2}-b t^{3} .\) The acceleration at…

The position \(x\) of a particle varies with time \((t)\) as \(x=a t^{2}-b t^{3} .\) The acceleration at time \(t\) of the particle will be equal to zero, where \(t\) is equal to
  1. \(\frac{2 a}{3 b}\)
  2. \(\frac{a}{b}\)
  3. \(\frac{a}{3 b}\)
  4. zero

Solution

\(\begin{array}{l}
x=a t^{2}-b t^{3} \\
\text {velocity }=\frac{d x}{d t}=2 a t-3 b t^{2} \\
\text { and acceleration }=\frac{d}{d t}\left(\frac{d^{2} x}{d t^{2}}\right)=2 a-6 b t
\end{array}\)
Acceleration will be zero if
\(2 a-6 b t=0 \Rightarrow t=\frac{2 a}{6 b}=\frac{a}{3 b}\)

Asked in: JEE Mains - Motion In One Dimension - Chapter Test

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