The correct option is A 0.5
Given:
Initial velocity of m1,=v
Final velocity of m1,=−v/3
Initial velocity of m2,=0
From conservation of momentum
Pi=Pf
m1v+m2.0=m1(−v3)+m2v2
43m1v=m2v2
m1m2=3v24v ...(1)
Form energy conservation
12m1v2+12m2×(0)2=12m1(v3)2+12m2v22
12m1v2−118m1v2=12m2v22
8m1v218=12m2v22
89m1v2=m2v22
89m1m2=(v2v)2
v2v=√8m19m2
Now in equation (1)
m1m2=34×√8m19m2
m1m2=12=0.5
Hence, option (C) is correct.
OR
For elastic collision,
Velocity of m1 after collision is v1=m1−m2m1+m2u1+2m2m1+m2u2
As u1=v,u2=0 & v1=−v/3
−13=m1−m2m1+m2
−m1−m2=3m1−3m2
m1m2=12=0.5
Hence, option (C) is correct.