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Grade 12th passMechanics

prove the time period of conical equilibrium is independent of the mass suspended.

Profile image of Naresh Kumar Oad
9 Years agoGrade 12th pass
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ApprovedApproved Tutor Answer1 Year ago

To demonstrate that the time period of conical equilibrium is independent of the mass suspended, we can analyze the forces acting on a pendulum that is swinging in a conical motion. This scenario typically involves a mass attached to a string, which is fixed at one end and allowed to swing in a circular path while maintaining a constant angle with respect to the vertical. Let's break this down step by step.

Understanding the Forces at Play

When a mass \( m \) is suspended from a string of length \( L \) and swings in a conical motion, two primary forces act on it:

  • Tension (T): The force exerted by the string, directed along its length.
  • Gravitational Force (mg): The weight of the mass acting downward.

Analyzing the Motion

In conical equilibrium, the mass moves in a horizontal circle while the string makes a constant angle \( \theta \) with the vertical. The tension can be resolved into two components:

  • The vertical component, which balances the weight: \( T \cos(\theta) = mg \)
  • The horizontal component, which provides the centripetal force necessary for circular motion: \( T \sin(\theta) = \frac{mv^2}{r} \)

Here, \( r \) is the radius of the circular path, given by \( r = L \sin(\theta) \), and \( v \) is the linear speed of the mass.

Deriving the Time Period

To find the time period \( T \) of the conical motion, we first express the linear speed \( v \) in terms of the angular speed \( \omega \):

Since \( v = r \omega \), we can substitute \( r \) to get:

\( v = L \sin(\theta) \omega \)

Substituting this into the centripetal force equation gives us:

\( T \sin(\theta) = \frac{m(L \sin(\theta) \omega)^2}{L \sin(\theta)} \)

After simplifying, we find:

\( T \sin(\theta) = m L \sin(\theta) \omega^2 \)

From the vertical force balance, we have \( T = \frac{mg}{\cos(\theta)} \). Substituting this into the equation yields:

\( \frac{mg}{\cos(\theta)} \sin(\theta) = m L \sin(\theta) \omega^2 \)

Canceling \( m \) (assuming \( m \neq 0 \)) and rearranging gives:

\( g \tan(\theta) = L \omega^2 \)

Finding the Time Period

Now, the angular speed \( \omega \) is related to the time period \( T \) by the formula:

\( \omega = \frac{2\pi}{T} \)

Substituting this into our previous equation results in:

\( g \tan(\theta) = \frac{L (2\pi)^2}{T^2} \)

Rearranging for \( T^2 \) gives:

\( T^2 = \frac{4\pi^2 L \cos(\theta)}{g \sin(\theta)} \)

This equation shows that the time period \( T \) depends only on the length of the string \( L \), the angle \( \theta \), and the acceleration due to gravity \( g \). Notably, there is no \( m \) in this expression, indicating that the time period is indeed independent of the mass suspended.

Conclusion

In summary, through the analysis of forces and the derivation of the time period formula, we have shown that the time period of conical equilibrium is independent of the mass of the object. This result highlights an interesting aspect of pendulum dynamics, where the mass does not influence the time it takes to complete one full cycle of motion.