Two point charges Q and q are placed at distance r and `r/2` respectively alogn a straigt line from a third charge 4q. If q is in equilibrium determine `Q/q`.

Explanation

To solve the problem, we need to analyze the forces acting on the charge \( q \) due to the other two charges \( Q \) and \( 4q \). The charge \( q \) is in equilibrium, which means that the net force acting on it must be zero.

### Step-by-Step Solution:

1. **Identify the Forces Acting on Charge \( q \)**:
- The force acting on charge \( q \) due to charge \( Q \) (which is at a distance \( r \)) will be repulsive since both charges are positive.
- The force acting on charge \( q \) due to charge \( 4q \) (which is at a distance \( r/2 \)) will also be repulsive.

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