Easy MCQ +4 / -1 PYQ · JEE Mains 2021

The instantaneous velocity of a particle moving in a straight line is given as $V = \alpha t + \beta {t^2}$, where $\alpha$ and $\beta$ are constants. The distance travelled by the particle between 1s and 2s is :

  1. A 3$\alpha$ + 7$\beta$
  2. B ${3 \over 2}\alpha + {7 \over 3}\beta$ Correct answer
  3. C ${\alpha \over 2} + {\beta \over 3}$
  4. D ${3 \over 2}\alpha + {7 \over 2}\beta$

Solution

$V = \alpha t + \beta {t^2}$<br><br>${{ds} \over {dt}} = \alpha t + \beta {t^2}$<br><br>$\int\limits_{{S_1}}^{{S_2}} {ds = \int\limits_1^2 {(\alpha t + \beta {t^2})dt} }$<br><br>$${S_2} - {S_1} = \left[ {{{\alpha {t^2}} \over 2} + {{\beta {t^3}} \over 3}} \right]_1^2$$<br><br>As particle is not changing direction <br><br>So distance = displacement<br><br>Distance = $\left[ {{{\alpha [4 - 1]} \over 2} + {{\beta [8 - 1]} \over 3}} \right]$<br><br>$= {{3\alpha } \over 2} + {{7\beta } \over 3}$

About this question

Subject: Physics · Chapter: Kinematics · Topic: Motion in a Straight Line

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