Given, bodies are thrown with speed u1 and u2, i.e. u1=u2=10ms−1. One is vertically up, i.e. 90∘ with horizontal, and other is thrown at angle θ with vertical, i.e. θ=60∘. If required time, t=2s.
Now, s12 be the relative position of 1 with respect to 2 and v12 be the relative speed of 1 with respect to 2 . As we know that, Formula of resultant vector v1 and v2 by using triangle law, v12=√v12+v22−2v1v2‌cos‌θ =√102+102−2(10)2×cos‌60∘ =√200−200×‌