To determine between which two objects the gravitational attraction is the greatest when placed 1 meter apart, we can use Newton's law of universal gravitation, which states that the gravitational force \( F \) between two objects is directly proportional to the product of their masses \( m_1 \) and \( m_2 \) and inversely proportional to the square of the distance \( r \) between them:
\[ F = G \frac{m_1 m_2}{r^2} \]
Since the distance is constant (1 meter in this case), we can compare the products of the masses of the objects.
Let's calculate the mass products for each pair of objects:
- Paper clip and penny: \( 1.0 \times 2.5 = 2.5 \) grams²
- Penny and small pot: \( 2.5 \times 1200 = 3000 \) grams²
- Small pot and book: \( 1200 \times 860 = 1,032,000 \) grams²
- Book and cereal box: \( 860 \times 500 = 430,000 \) grams²
Now, let's compare the products:
- Paper clip and penny: 2.5 grams²
- Penny and small pot: 3000 grams²
- Small pot and book: 1,032,000 grams²
- Book and cereal box: 430,000 grams²
The greatest gravitational attraction, therefore, is between the small pot and the book (1,032,000 grams²).
So the answer is: between the small pot and the book.