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| 1. |
A particle is projected with velocity 20 m/s, so that it just clears two walls of equal height 10 m, which are at a distance 20 m from each other. The time of passing between the walls is |
| Answer» TION:Correct option isA2sLet t be the time of passing between the wallsS=vt20=20cosθt -------------(i)verticallyv 2 =u 2 +2aSv 2 =u 2 sin 2 θ−2g×10v 2 =u 2 sin 2 θ−20gv=u+at0=u−gtt= gv ------------------(II)equating EQ i and iicosθ1 =2 gv SQUARING both sides and SUBSTITUTING vcos 2 θg 2 =4u 2 sin 2 θ−80glet sin 2 θ be xg 2 =16g 2 x(1−x)−8g 2 (1−x)9=16x−16x 2 +8x16x 2 −24x+9=0(4x−3) 2 =0 x= 43sin 2 θ= 43θ= 3 πtherefore time of passing between the wallst= cosθ1 =2s | |