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Concepts Of Physics MCQ Edition [Volume 1]
Exam
Concepts Of Physics MCQ Edition [Volume 1]
Subject
Physics
Chapter
Rotational Mechanics

Concepts Of Physics MCQ Edition [Volume 1] · Physics · Rotational Mechanics

A uniform rod of mass m and length l is struck at one end by a...

A uniform rod of mass mm and length ll is struck at one end by a force FF perpendicular to the rod for a short duration tt. Assuming tt is small enough that the rod does not appreciably alter its direction while the force acts, determine the speed of the centre of mass after the force has stopped acting.

Options

  1. AFt2m\dfrac{Ft}{2m}
  2. BFtm\dfrac{Ft}{m}
  3. CFtml\dfrac{Ft}{ml}
  4. D2Ftm\dfrac{2Ft}{m}

Correct answer

B. Ftm\dfrac{Ft}{m}

Step-by-step solution

The impulse delivered to the rod is given by the product of the force and the time duration:

J=FtJ = Ft

According to the impulse-momentum theorem, the net linear impulse applied to a system is equal to the change in its linear momentum. The point of application of the force affects the angular velocity but does not affect the linear velocity of the centre of mass.

J=ΔpcmJ = \Delta p_{cm}

Ft=mvcm−0Ft = m v_{cm} - 0

vcm=Ftmv_{cm} = \dfrac{Ft}{m}
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