A projectile is thrown with a velocity of 20 m / s , at an angle of 60 ° with the horizontal. After how much time the velocity vector will make an angle of 45 ° with the horizontal

Question

A projectile is thrown with a velocity of 20 m / s , at an angle of 60 ° with the horizontal. After how much time the velocity vector will make an angle of 45 ° with the horizontal, 3 s, 1 3 s, 3 + 1 s, 3 - 1 s

MARKS App · Accepted Answer

As the horizontal component is the same for a projectile Let projectile velocity is v when particle makes angle 45 ° with horizontal, hence v = u cos ⁡ θ sec ⁡ ϕ = 20 cos ⁡ 60 ° sec ⁡ 45 ° v = 20 . 1 2 . 2 = 10 2 m / s t = v y - u y g = 10 3 - 10 10 = 3 - 1 s

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