ISRO Mechanical & Aerospace 2011 - Question 19

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A particle starts from rest with a constant acceleration $\alpha$ m/sec$^2$ and after some time it decelerates at a uniform rate of $\beta$ m/sec$^2$ till it comes to rest. If the total time taken between two rests positions is t, the maximum velocity acquired by the particle would be

  • A. $\frac{\alpha + \beta}{2}t$
  • B. $\frac{\alpha - \beta}{2}t$
  • C. $\left(\frac{\alpha\beta}{\alpha+\beta}\right)t$
  • D. $\left(\frac{\alpha+\beta}{\alpha\beta}\right)t$

Answer: C. $\left(\frac{\alpha\beta}{\alpha+\beta}\right)t$

Explanation: $V_{max} = t_1 \alpha = t_2 \beta$. Total time $t = t_1 + t_2 = V_{max}/\alpha + V_{max}/\beta$. Solving for $V_{max}$ gives the result.

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