An empty plastic box of mass sm is found to accelerate up at the rate of g/6 when placed deep inside water. How much sand should be put inside the box so tht it may accelerate down at the rate of g/6?

Explanation

To solve the problem, we need to analyze the forces acting on the plastic box when it is submerged in water and how the addition of sand affects its acceleration.

### Step-by-Step Solution:

1. **Understanding the Initial Condition**:
- The mass of the empty plastic box is \( m \).
- The box accelerates upward with an acceleration of \( \frac{g}{6} \) when submerged in water.

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