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An object of mass m swings in a horizontal circle on a string of length L that tilts downward at angle θ.


Find an expression for the angular velocity ω in terms of g, L and angle θ.

Verified Answer :

Let g, r, L and T are  gravity, radius, length, and angle of string w/r/t vertical, respectively. 
Then
ω²r = rg/Lcos T

ω² = g/L cos T
ω = √(g / L cos T) 

Answer:

The expression would be ω = \(\sqrt{\frac{g}{L sin 0 } }\)

Explanation:

Given that ω is the angular velocity

g is the acceleration due to gravity

L is the length

θ is the angle of downward tilt

For an object we compare the horizontal and vertical component of the forces acting on the body;

For vertical component

T sinθ = mg............1

For the horizontal component

T cos θ = \(\frac{mv^{2} }{R}\) .............2

R is our radius and is  = L cos θ

v = ωR

substituting into equation 2 we have

T cos θ = m(ωR\()^{2}\) /R

T cos θ=m(ω\()^{2}\)R ..................3

Now comparing the vertical and the horizontal component we have;

equation 1 divided by equation 3 we have

T sin θ /T cos θ = mg / m(ω\()^{2}\)R

Tan θ = g / (ω\()^{2}\)R............4

Making ω the subject formula we have;

(ω\()^{2}\) = g/  R Tan θ

But R = L cos θ and Tan θ = sin θ/ cosθ

putting into equation 4 we have;

(ω\()^{2}\) = g /[( L cos θ) x( sin θ/ cosθ)]

(ω\()^{2}\) = g/ L sinθ

ω = \(\sqrt{\frac{g}{L sin 0 } }\)

Therefor the expression for the angular velocity ω in terms of g, L and angle θ would be ω = \(\sqrt{\frac{g}{L sin 0 } }\)