Verified Solution • 2025–26 Session moderate

QJEEM19Phff86: JEE Main 2019 Physics - Class 11 JEEM19Phff86 Solution: A force acts on a 2 kg object so that its position is given as…

A force acts on a 2 kg object so that its position is given as a function of time as x = 3t2 + 5. What is the work done by this force in first 5 seconds ?

Multiple Choice Options

  • A 850 J
  • B 950 J
  • C 875 J
  • D 900 J

Step-by-Step Verified Solution

Displacement,

x = 3t2 + 5

∴  v = dxdt=6t

At t = 0,   velocity = 6 × 0 = 0

at t = 5, velocity = 5 × 6 = 30 m/s

we know from work energy theorem,

Work (W) = change in kinetic energy (ΔK)

= 12mvF2−12mvi2

= 12 × 2 × (30)2 − 0

= 900 J

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