Assuming particle_1 is dropped at t=0 s
therefore at t=2 s
h1=u1t+12gt2
h1=12×10×4
h1=20 m
h2=uv(t−1)+1/2g(t−1)2
h2=1/2×10×1
h2=5m
relative verticle displacement = h1−h2=15m
Now, horizontal displacement of 1 is zero.
R1=0
R2=uh(t−1)=10×1=10m
relative horizontal displacement=R2−R1=10m
relative horizontal velocity urh=uh−0=10m/s since for particle 1 horizontal velocity is zero.
Now verticle velocity of 2 at t=2s
uv=u2v+g(t−1)=10m/s
and u1=u1v+gt=20m/s
therefore,relative vertical velocity urv=u1−uv=10m/s
therefore,
A→1
B→4
C→1
D→1