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NTA Abhyas 2020
Exam
NTA Abhyas
Year
2020
Subject
Physics
Chapter
Motion in Two Dimensions

NTA Abhyas 2020 · Physics · Motion in Two Dimensions

A boy throws a ball at an angle θ with the vertical. If the...

A boy throws a ball at an angle θ\theta with the vertical. If the vertical component of the initial velocity is 20ms−120m{s}^{- 1} and the wind imparts a horizontal acceleration of 8ms−28m{s}^{- 2} to the left, the angle at which the ball must be thrown so that the ball returns to the boy's hand is θ\theta. What is the value of 10(tanθ)10\left(tan \theta\right)?

Correct answer

8

Step-by-step solution

Taking the upward vertical as positive y-direction

uy=20ms−1{u}_{y} = 20m{s}^{- 1}

ay=−10ms−2{a}_{y} = - 10m{s}^{- 2}

sy=uyt+12ayt2{s}_{y} = {u}_{y}t + \dfrac{1}{2}{a}_{y}{t}^{2}

t=2uyay=2×2010=4st = \dfrac{2{u}_{y}}{{a}_{y}} = \dfrac{2 \times 20}{10} = 4s

Taking the right-side horizontal as positive x-direction

sx=0=uxt+12ax×t2{s}_{x} = 0 = {u}_{x}t + \dfrac{1}{2}{a}_{x} \times {t}^{2}

0=ux(4)−82(4)20 = {u}_{x}\left(4\right) - \dfrac{8}{2}{\left(4\right)}^{2}

ux=16{u}_{x} = 16

tanθ=uxuy=1620tan \theta = \dfrac{{u}_{x}}{{u}_{y}} = \dfrac{16}{20}

10tanθ=10×1620=810tan \theta = 10 \times \dfrac{16}{20} = 8
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