SIR PLZ CLEAR MY DOUBT FOR THIS QUESTION I HAVE ASKED THIS QUESTION ALREADY BUT THE ANSWER GIVEN TO ME WAS NOT HELP FULL . A particle was projected with initial velocity 20m/s at 60 degree to horizontal. After what time its velocity will be perpendicular to initial direction of motion . CHAPTER NAME - VECTOR

Dear student
 strategy :  first write the initial velocity in vector form u                   : then write the final velcity after time t when particle makes makes angle 900 with u let v                       :last make dot product of u. v=0 which gives you t as below u=20cos600i^+20sin600j^=10i^+103j^v=u+at=10i^+103j^+10t(-j)=10i^+(103-10t)j^(10i^+103j^).{10i^+(103-10t)j^}=0100+300=1003tt=43 secRegards

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