Projectile Motion Question

Round off the answer to the nearest integer


The answer is 18.

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2 solutions

Hongqi Wang
Nov 4, 2020

v t 2 v 0 2 = 2 a s v t = 2 a s + v 0 2 = 2 a s + ( v c o s 5 3 ) 2 = 2 × 10 × 40 + 6 2 = 836 v_t^2 - v_0^2 = 2as \\ v_t = \sqrt {2as + v_0^2} \\ = \sqrt {2as + (v \cdot cos {53^{\circ}})^2} \\ = \sqrt {2 \times 10 \times 40 + 6^2} \\ = \sqrt {836}

t = v t v 0 a = 836 6 10 t = \frac {v_t - v_0}a = \frac {\sqrt {836} - 6}{10}

s = v t = v s i n 5 3 t = 10 × s i n 5 3 × 836 6 10 = 18.33 s = vt = v \cdot sin {53^{\circ}} \cdot t \\ = 10 \times sin {53^{\circ}} \times \frac {\sqrt {836} - 6}{10} \\ = 18.33

Considering time and height relation

Or , ( 40 0 ) = ( 10 c o s 53 ° ) t 5 t ² . (-40-0) = - (10 cos 53°) t-5 t². (Take g=-10 m/s² , cos 53° =0.6 )

Or , 5 t ² + 6 t 40 = 0 5t²+6t -40 =0

      ≈t=2.291366 s

Distance covered = (velocity in horizontal direction )× t t

      = 10 sin 53° × 2.291366 ≈  18.330932  (approx )

lost t t in term v t vt

Hongqi Wang - 7 months, 1 week ago

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Thanking you. That was typo

Dwaipayan Shikari - 7 months, 1 week ago

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