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Motion in A Straight Line question

2025 · 3 Apr · Shift 2 · Q53
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  5. /2025 · 3 Apr · Shift 2 · Q53

Motion in A Straight Line question

2025 · 3 Apr · Shift 2 · Q53

JEE MainPhysicsMotion in A Straight LineMCQ+4 / −1
A particle moves along the xxx-axis and has its displacement xxx varying with time t according to the equation: x=c0(t2−2)+c(t−2)2x=\mathrm{c}_0\left(\mathrm{t}^2-2\right)+\mathrm{c}(\mathrm{t}-2)^2x=c0​(t2−2)+c(t−2)2 where c0\mathrm{c}_0c0​ and c are constants of appropriate dimensions. Then, which of the following statements is correct?
  1. A
    the acceleration of the particle is 2(c+c0)2\left(c+c_0\right)2(c+c0​)
  2. B
    the acceleration of the particle is 2c02 c_02c0​
  3. C
    the acceleration of the particle is 2 c
  4. D
    the initial velocity of the particle is 4c4 c4c
View written solutionFree

Correct answer: A

  1. Given displacement equation

    x=c0(t2−2)+c(t−2)2x=c_0(t^2-2)+c(t-2)^2x=c0​(t2−2)+c(t−2)2

  2. Expand the expression

    First expand (t−2)2(t-2)^2(t−2)2:

    (t−2)2=t2−4t+4(t-2)^2=t^2-4t+4(t−2)2=t2−4t+4

    So,

    x=c0(t2−2)+c(t2−4t+4)x=c_0(t^2-2)+c(t^2-4t+4)x=c0​(t2−2)+c(t2−4t+4)

    x=c0t2−2c0+ct2−4ct+4cx=c_0t^2-2c_0+ct^2-4ct+4cx=c0​t2−2c0​+ct2−4ct+4c

    x=(c0+c)t2−4ct+(4c−2c0)x=(c_0+c)t^2-4ct+(4c-2c_0)x=(c0​+c)t2−4ct+(4c−2c0​)

  3. Find velocity

    Velocity is

    v=dxdtv=\frac{dx}{dt}v=dtdx​

    Therefore,

    v=2(c0+c)t−4cv=2(c_0+c)t-4cv=2(c0​+c)t−4c

  4. Find acceleration

    Acceleration is

    a=dvdt=d2xdt2a=\frac{dv}{dt}=\frac{d^2x}{dt^2}a=dtdv​=dt2d2x​

    Hence,

    a=2(c0+c)a=2(c_0+c)a=2(c0​+c)

  5. Check the options

    • A: acceleration is 2(c+c0)2(c+c_0)2(c+c0​) ✅ Correct

    • B: acceleration is 2c02c_02c0​ ❌ Incomplete

    • C: acceleration is 2c2c2c ❌ Incomplete

    • D: initial velocity is 4c4c4c ❌ Since at t=0t=0t=0,

      v(0)=2(c0+c)(0)−4c=−4cv(0)=2(c_0+c)(0)-4c=-4cv(0)=2(c0​+c)(0)−4c=−4c

      so initial velocity is −4c-4c−4c, not 4c4c4c.

  6. Conclusion

    The correct option is:

    A\boxed{A}A​

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