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Grade 11Mechanics

A particle is projected with velocity u at angle theta with horizontal find the time when velocity vector is perpendicular to intial velocity vector

Profile image of G .harrish
7 Years agoGrade 11
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2 Answers

Profile image of Eshan
7 Years ago
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Profile image of Piyush Kumar Maurya
7 Years ago
Initial velocity = u
u = u+ uy
u = ucos theta i cap+ usin theta j cap
Here uremains constant throughout the journey.
Velcity at time t = v
V= ucos theta 
V= usin theta - gt
V(t) = ucos theta i cap + (usin theta - gt) j cap
 
Now for V(t) to be perpendicular to u , their dot product should be zero.
 So , V(t) . u = 0
       [ ucos theta i cap + ( usin theta - gt) j cap] .               (ucos theta i cap + usin theta j cap) = 0 
> ucos^2 theta + usin^2 theta - usin theta *gt = 0
 >  t= u / sin theta *g