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JEE Main 202228 JuneEvening Shift
Exam
JEE Main
Year
2022
Date
28 June
Shift
Evening Shift
Subject
Physics
Chapter
Motion in Two Dimensions

JEE Main 2022 · 28 June · Evening Shift · Physics · Motion in Two Dimensions

A ball is spun with angular acceleration α = 6 t ^ 2 - 2t where t...

A ball is spun with angular acceleration α=6t2−2t\alpha = 6{t}^{2} - 2t where tt is in second and α\alpha is in rads−2rad{s}^{- 2}. At t=0t = 0, the ball has angular velocity of 10rads−110rad{s}^{- 1} and angular position of 4rad4rad. The most appropriate expression for the angular position of the ball is

Options

  1. A32t4−t2+10t\dfrac{3}{2}{t}^{4} - {t}^{2} + 10t
  2. Bt42−t33+10t+4\dfrac{{t}^{4}}{2} - \dfrac{{t}^{3}}{3} + 10t + 4
  3. C2t43−t36+10t+12\dfrac{2{t}^{4}}{3} - \dfrac{{t}^{3}}{6} + 10t + 12
  4. D2t4−t32+5t+42{t}^{4} - \dfrac{{t}^{3}}{2} + 5t + 4

Correct answer

B. t42−t33+10t+4\dfrac{{t}^{4}}{2} - \dfrac{{t}^{3}}{3} + 10t + 4

Step-by-step solution

Given: α=6t2−2t\alpha = 6{t}^{2} - 2t

Using relation α=dωdt=6t2−2t\alpha = \dfrac{d \omega}{d t} = 6{t}^{2} - 2t

Integrating the above,

∫10ωdω=∫0t(6t2−2t)dt{∫}_{10}^{\omega} d \omega = {∫}_{0}^{t}\left(6{t}^{2} - 2t\right) d t

⇒ω−10=2t3−t2⇒ \omega - 10 = 2{t}^{3} - {t}^{2}

Now, ω=dθdt=10+2t3−t2\omega = \dfrac{d \theta}{d t} = 10 + 2{t}^{3} - {t}^{2}

∫4θdθ=∫0t(10+2t3−t2)dt{∫}_{4}^{\theta} d \theta = {∫}_{0}^{t}\left(10 + 2{t}^{3} - {t}^{2}\right) d t

Integrating the above relation,

θ−4=10t+t42−t33\theta - 4 = 10t + \dfrac{{t}^{4}}{2} - \dfrac{{t}^{3}}{3}

Thus, angular position of the ball is θ=t42−t33+10t+4\theta = \dfrac{{t}^{4}}{2} - \dfrac{{t}^{3}}{3} + 10t + 4.

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