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Near the surface of Earth an electric field points radially downward and has a magnitude of approximately 100 N/C. What charge (magnitude and sign) would have to be placed on a penny that has a mass of 3g to cause it to rise into the air with an upqard acceleration of 0.19 m/s^2

Respuesta :

Answer:

[tex]q=2.997\times 10^{-4}[/tex]C

Sign-Negative

Explanation:

We are given that

Electric field =[tex]E=100NC^{-1}[/tex] (Radially downward)

Acceleration=[tex]0.19 ms^{-2}[/tex](Upward)

Mass of charge=3 g=[tex]3\times 10^{-3}[/tex]kg

1kg=1000g

We have to find the magnitude and sign of  charge would have to be placed on a penny .

By newton's second law

[tex]\sum F_y=ma[/tex]

[tex]\sum F_y=qE-mg[/tex]

Substitute the values then we get

[tex]qE-mg=ma[/tex]

Substitute the values then we get

[tex]q(100)-3\times 10^{-3}(9.8)=3\times 10^{-3}(0.19)[/tex]

[tex]100q-29.4\times 10^{-3}=0.57\times 10^{-3}[/tex]

[tex]100q=0.57\times 10^{-3}+29.4\times 10^{-3}=29.97\times 10^{-3}[/tex]

[tex]q=\frac{29.97\times 10^{-3}}{100}[/tex]

[tex]q=2.997\times 10^{-4}[/tex]C

Sign of charge =Negative

Because electric force acting  in opposite direction of electric field therefore,charge on penny will be negative.