Question

Q4. The figure below shows two negatively charged objects (with the same charge) and one positively charged object. What is the direction of the net electric force on the positively charged object? A. Horizontal to the Left B. Horizontal to the Right C. Force is zero D. None of the above

Answer 1

Electrostatic force is give by

F = k*q1*q2/r^2

force is attractive if both charge have same signs, and force is repulsive if both charge have same sign.

Force on +ve charge (q) due to left -ve charge (q1) will be towards the charge in left side (-ve x-axis)

Force on +ve charge (q) due to right -ve charge (q2) will be towards the charge in right side (+ve x-axis)

So net force on +ve charge will be

Fnet = F2 - F1

Assuming that figure is accurate we can see that left negative charge is near the positive charge and right negative charge is away from positive charge compare to that.

d1 = distance between +ve charge and left -ve charge

d2 = distance between +ve charge and right -ve charge

here d2 > d1 (from the figure)

Fnet = k*q*q2/d2^2 - k*q*q1/d1^2

Since given that q1 = q2 = Q

Fnet = k*q*Q*(1/d2^2 - 1/d1^2)

Fnet = [k*q*Q/(d1^2*d2^2)]*(d1^2 - d2^2)

since d2 > d1, So

d2^2 > d1^2

d1^2 - d2^2 < 0

Which means Fnet is negative, So Net force on the +ve charge will be towards the left side

Correct option is A.

Horizontal to the left

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