Discussion Forum

1)

Aeroplanes A and B are flying with constant velocity in the same vertical plane at angles 30°  and 60° with respect to the horizontal respectively as shown in the figure. The speed of A is   $100\sqrt{3}$ ms^-1. At time t=0 s, an observer in A Finds B at a distance of 500m. This observer sees B moving with a constant velocity perpendicular to the line of motion of A. If at t=t₀, A just escapes being hit by B, t₀ in seconds is 

Answer:

Option A

Explanation:

 The relative velocity of B with respect to A is perpendicular to line PA. Therefore, along line PA, velocity components of A and B should be the same.

$\Rightarrow$    $V_{A}=100\sqrt{3}=V_{B}\cos 30^{0}$

$\Rightarrow$   V_B=200m/s

$t_{0}=\frac{500}{V_{B}\sin 30^{0}}$

  $=\frac{500}{200\times\frac{1}{2}}=5s$