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A pendulum bob of mass 80mg …

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A pendulum bob of mass 80mg carrying a charge of 2 * 10-8 C is at rest in a horizontal uniform electric field of 2*10Vm-1.Find the tension in the thread of the pendulum and the angle it makes with the vertical.

  • 2 answers

Mayank Gautam 5 years, 3 months ago

K

Payal Singh 6 years, 9 months ago

Given: mass = 80 mg = 80 × 10-6 Kg

Charge q = 2 × 10-8 C

E = 2 × 104 Vm-1

Let T is tension in string and {tex}\theta{/tex}

is angle of string with vertical.

In equilibrium

{tex}Tsin\theta = qE \ ....(1){/tex}

{tex}Tcos\theta = mg \ ....(2){/tex}

Divide (1) by (2), we get

{tex}tan\theta = {qE\over mg}{/tex}

=> {tex}tan \theta = {2\times 10^{-8}\times 2\times 10^4\over 80\times 10^{-6}\times 10}{/tex}

=> {tex}tan \theta = 0.5{/tex}

=> {tex}\theta = 27^°{/tex}

Now Tension T = {tex}qE\over sin \theta{/tex}{tex}{2\times 10^{-8}\times 2\times 10^4\over sin 27^°}{/tex}

= 8.8 × 10-4 N

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