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Motion in A Straight Line question

2021 · 17 Mar · Shift 2 · Q54
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  5. /2021 · 17 Mar · Shift 2 · Q54

Motion in A Straight Line question

2021 · 17 Mar · Shift 2 · Q54

JEE MainPhysicsMotion in A Straight LineMCQ+4 / −1
The velocity of a particle is v = v0 + gt + Ft2. Its position is x = 0 at t = 0; then its displacement after time (t = 1) is :
  1. A
    v0 + g + f
  2. B
    v0 + g2{g \over 2}2g​+F3{F \over 3}3F​
  3. C
    v0 + 2g + 3F
  4. D
    v0 + g2{g \over 2}2g​ + F
View written solutionFree

Correct answer: B

  1. The velocity is given as v(t)=v0+gt+Ft2.v(t)=v_0+gt+Ft^2.v(t)=v0​+gt+Ft2.

  2. Displacement is obtained by integrating velocity with respect to time: x(t)−x(0)=∫0tv(t) dt.x(t)-x(0)=\int_0^t v(t)\,dt.x(t)−x(0)=∫0t​v(t)dt.

  3. Since x(0)=0x(0)=0x(0)=0, the displacement after time t=1t=1t=1 is x(1)=∫01(v0+gt+Ft2) dt.x(1)=\int_0^1 (v_0+gt+Ft^2)\,dt.x(1)=∫01​(v0​+gt+Ft2)dt.

  4. Integrate term by term: ∫01v0 dt=v0,\int_0^1 v_0\,dt=v_0,∫01​v0​dt=v0​, ∫01gt dt=g[t22]01=g2,\int_0^1 gt\,dt=g\left[\frac{t^2}{2}\right]_0^1=\frac{g}{2},∫01​gtdt=g[2t2​]01​=2g​, ∫01Ft2 dt=F[t33]01=F3.\int_0^1 Ft^2\,dt=F\left[\frac{t^3}{3}\right]_0^1=\frac{F}{3}.∫01​Ft2dt=F[3t3​]01​=3F​.

  5. Therefore, x(1)=v0+g2+F3.x(1)=v_0+\frac{g}{2}+\frac{F}{3}.x(1)=v0​+2g​+3F​.

  6. Comparing with the options:

    • A: v0+g+Fv_0+g+Fv0​+g+F ❌
    • B: v0+g2+F3v_0+\frac{g}{2}+\frac{F}{3}v0​+2g​+3F​ ✅
    • C: v0+2g+3Fv_0+2g+3Fv0​+2g+3F ❌
    • D: v0+g2+Fv_0+\frac{g}{2}+Fv0​+2g​+F ❌

Hence, the correct answer is Option B.

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