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Grade 11Mechanics

i want to drive the equation of time period of pendulum in inclined plane??

Profile image of kanishak garg
9 Years agoGrade 11
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Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

To derive the equation for the time period of a pendulum on an inclined plane, we first need to understand how the forces acting on the pendulum change when it is not hanging vertically. The time period of a simple pendulum is influenced by its length and the acceleration due to gravity, but when the pendulum is on an incline, the effective gravitational force acting on it changes. Let’s break this down step by step.

Understanding the Forces at Play

When a pendulum swings on an inclined plane, the gravitational force can be resolved into two components: one acting perpendicular to the incline and the other acting parallel to it. The component of gravitational force that influences the motion of the pendulum is the one acting parallel to the incline.

Resolving Gravitational Forces

Consider a pendulum of length L making an angle θ with the vertical. The gravitational force acting on the pendulum bob is mg, where m is the mass of the bob and g is the acceleration due to gravity. The forces can be resolved as follows:

  • The component of gravitational force acting parallel to the incline: F_parallel = mg \sin(θ)
  • The component acting perpendicular to the incline: F_perpendicular = mg \cos(θ)

Setting Up the Equation of Motion

The restoring force that brings the pendulum back to its equilibrium position is the parallel component of the gravitational force. According to Newton's second law, this force can be expressed as:

F = ma

Substituting the expression for the restoring force, we have:

mg \sin(θ) = ma

Here, a is the angular acceleration of the pendulum. Since a can also be expressed in terms of angular displacement θ and the length of the pendulum L, we can relate them as follows:

a = -\frac{g \sin(θ)}{L} \cdot \theta

Deriving the Time Period

For small angles, we can approximate sin(θ) ≈ θ (in radians). Thus, the equation simplifies to:

mg \theta = mL \frac{d^2\theta}{dt^2}

Rearranging gives us:

\frac{d^2\theta}{dt^2} + \frac{g \sin(θ)}{L} \theta = 0

For small angles, this further simplifies to:

\frac{d^2\theta}{dt^2} + \frac{g}{L} \theta = 0

Finalizing the Time Period Formula

This is a simple harmonic motion equation, where the angular frequency ω is given by:

ω = \sqrt{\frac{g}{L}}

The time period T of a simple harmonic oscillator is related to the angular frequency by:

T = \frac{2\pi}{ω} = 2\pi \sqrt{\frac{L}{g}}

Adjusting for Inclination

However, since we are on an incline, we need to consider the effective gravitational acceleration, which is g \sin(θ). Therefore, the time period of a pendulum on an inclined plane becomes:

T = 2\pi \sqrt{\frac{L \cos(θ)}{g}}

This equation shows how the time period of a pendulum changes when it is placed on an inclined plane, depending on the angle of inclination and the length of the pendulum. The cosine factor accounts for the change in the effective gravitational force acting on the pendulum.