1.

A charged ball of mass 9 kg is suspended from a string in a uniform elelctric field vecE = (3hati + 5hatj) xx 10^5 N//C. The ball is in equilibrium with theta=37^@. If direction of electric field is reversed, fing the new equilibrium position of the ball. Given your answer in terms of angle made by string with vertical. Take g = 10ms^(-2).

Answer»

`TAN^(-1)(3/4)`
`cot^(-1) (3/14)`
`cot^(-1) (3/4)`
`tan^(-1)(3/14)`

Solution :
`Tsin theta=3thetaxx10^(5)`(i)
`Tcostheta=mg-5qxx10^(5)`(ii)
Solve to get `q=100muC,T=50N`.
After the rever4sal of direction of electric FIELD

`T'sin a=3qxx10^(5)` or `T'cos a=mg+5qxx10^(5))`
`TANA=(3qxx10^(5))`
`=(3XX10^(-4)xx10^(5))/(9xx10+5xx10^(-4)xx10^(5))=(3)/(14)`
or `a=tan^(-1)((3)/(14))`


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