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NEET PHYSICSWORK, ENERGY AND POWERMedium

Question

A particle of mass mm is driven by a machine that delivers a constant power of kk watts. If the particle starts from rest, the force on the particle at the time tt is:

A

mk2t1/2\sqrt{\frac{mk}{2}} t^{-1/2}

B

mkt1/2\sqrt{mk} t^{-1/2}

C

2mkt1/2\sqrt{2mk} t^{-1/2}

D

12mkt1/2\frac{1}{2} \sqrt{mk} t^{-1/2}

Step-by-Step Solution

To find the force as a function of time, we utilize the relationship between power, work, and kinetic energy:

  1. Work-Energy Theorem: Since the machine delivers constant power kk, the work done (WW) on the particle in time tt is W=P×t=ktW = P \times t = kt . According to the work-energy theorem, this work is equal to the change in kinetic energy: kt=12mv20kt = \frac{1}{2}mv^2 - 0 .
  2. Velocity Calculation: From the energy equation, we solve for velocity (vv): v2=2ktm    v=2ktmv^2 = \frac{2kt}{m} \implies v = \sqrt{\frac{2kt}{m}} .
  3. Force Calculation: Power is defined as the product of force and velocity (P=FvP = F \cdot v) . Therefore, F=PvF = \frac{P}{v}.
  4. Substitution: Substituting the expressions for PP and vv: F=k2ktm=k2m2kt=mk2t1/2F = \frac{k}{\sqrt{\frac{2kt}{m}}} = \sqrt{\frac{k^2 \cdot m}{2kt}} = \sqrt{\frac{mk}{2}} t^{-1/2}

Thus, the force acting on the particle at time tt is mk2t1/2\sqrt{\frac{mk}{2}} t^{-1/2}.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from WORK, ENERGY AND POWER. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWORK, ENERGY AND POWERparticledrivenmachinedeliversconstant

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