The speed of a projectile at its maximum height is half of its initial speed. The angle of projection is

The speed of a projectile at its maximum height is half of its initial speed. The angle of projection is
  1. $60^{\circ}$
  2. $15^{\circ}$
  3. $30^{\circ}$
  4. $45^{\circ}$

Solution

The speed of a projectile at its maximum height $\begin{aligned} \mathrm{v}^{\prime} & =\mathrm{v}_0 \cos \theta \\ \frac{\mathrm{v}_0}{2} & =\mathrm{v}_0 \cos \theta \\ \cos \theta & =\frac{1}{2} \\ \theta & =60^{\circ} \end{aligned}$

Asked in: NEET 2010 (Mains)

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