It is possible to project a particle with a given velocity in two possible ways so as to make them pass…

It is possible to project a particle with a given velocity in two possible ways so as to make them pass through a point $p$ at a horizontal distance $r$ from the point of projection. If $t_1$ and $t_2$ are times taken to reach this point in two possible ways, then the product $t_1 t_2$ is proportional to
  1. $\frac{1}{r}$
  2. $r$
  3. $r^2$
  4. $\frac{1}{r^2}$

Solution

$\begin{aligned} & T_1=\frac{2 u \sin \theta}{g} \\ & \text { and } \quad T_2=\frac{2 u \cos \theta}{g} \\ & T_1 T_2=\frac{2 u^2 \sin \theta \cos \theta}{g}=\frac{2 r}{g} \\ & {\left[\because R=\frac{v^2 \sin 2 \theta}{g}\right]} \\ & \end{aligned}$

Asked in: AP EAMCET 2012

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