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If the coefficient of friction between an ant and bowl is µ and the radius of the bowl is r, find the maximum height to which the ant can crawl in the bowl?

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Johnny Storm , 13 Years ago
Grade 11
anser 1 Answers
Askiitians Tutor Team

To determine the maximum height an ant can crawl inside a bowl, we need to analyze the forces acting on the ant due to gravity and friction. The bowl's shape plays a crucial role in this scenario, as it affects how the ant can move upward without slipping. Let's break this down step by step.

Understanding the Forces at Play

The ant is climbing a bowl, which we can assume is a hemisphere for simplicity. The forces acting on the ant include:

  • Gravitational Force (Weight): This acts downward and is equal to the mass of the ant (m) multiplied by the acceleration due to gravity (g).
  • Normal Force: This acts perpendicular to the surface of the bowl at any point where the ant is located.
  • Frictional Force: This opposes the motion of the ant and is given by the product of the coefficient of friction (μ) and the normal force (N).

Setting Up the Problem

When the ant is at a height \( h \) in the bowl, we can relate this height to the radius \( r \) of the bowl using trigonometry. The angle \( \theta \) that the ant makes with the vertical can be defined as:

\[ \sin(\theta) = \frac{h}{r} \]

From this, we can express \( h \) as:

\[ h = r \sin(\theta) \]

Analyzing the Forces

At the point where the ant is about to slip, the maximum frictional force must equal the component of the gravitational force acting down the slope of the bowl. The gravitational force can be resolved into two components:

  • The component acting perpendicular to the surface: \( mg \cos(\theta) \)
  • The component acting parallel to the surface: \( mg \sin(\theta) \)

The normal force \( N \) is equal to the perpendicular component of the weight:

\[ N = mg \cos(\theta) \]

The maximum frictional force \( F_f \) that can act on the ant is given by:

\[ F_f = \mu N = \mu mg \cos(\theta) \]

Setting Up the Equation

For the ant to remain stationary while climbing, the frictional force must be greater than or equal to the gravitational force component acting down the slope:

\[ \mu mg \cos(\theta) \geq mg \sin(\theta) \]

We can simplify this equation by canceling \( mg \) from both sides (assuming \( m \neq 0 \)):

\[ \mu \cos(\theta) \geq \sin(\theta) \]

Finding the Maximum Height

Rearranging gives us:

\[ \frac{\sin(\theta)}{\cos(\theta)} \leq \mu \]

This can be rewritten using the tangent function:

\[ \tan(\theta) \leq \mu \]

From this, we can find the maximum angle \( \theta_{max} \) that the ant can climb:

\[ \theta_{max} = \tan^{-1}(\mu) \]

Now, substituting back to find the maximum height \( h_{max} \):

\[ h_{max} = r \sin(\theta_{max}) = r \sin(\tan^{-1}(\mu)) \]

Final Expression for Maximum Height

Using the identity \( \sin(\tan^{-1}(x)) = \frac{x}{\sqrt{1+x^2}} \), we can express \( h_{max} \) as:

\[ h_{max} = r \cdot \frac{\mu}{\sqrt{1+\mu^2}} \]

This formula gives us the maximum height to which the ant can crawl inside the bowl, depending on the radius of the bowl and the coefficient of friction between the ant and the bowl's surface.

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