JAMB Physics 2016 Paper

Concept:At maximum height, the vertical component of velocity becomes zero. Time to reach this point depends only on initial vertical velocity and gravitational acceleration.Explanation:Initial velocity $u = 300\ \mathrm{m\,s^{-1}}$ and angle $\theta = 30^\circ$.Vertical component: $u_y = u \sin\theta = 300 \sin 30^\circ = 300 \times 0.5 = 150\ \mathrm{m\,s^{-1}}$.Time to maximum height is given by $t = \frac{u_y}{g}$.Substitute values: $t = \frac{150}{10} = 15\ \mathrm{s}$.This is half of total time of flight $\frac{2u\sin\theta}{g}$, confirming the result.Answer:$15\ \mathrm{s}$, so the correct option is D.