Question

Two short bar magnets with pole strengths of 900 ab-amp $\times$ cm and 100 ab-amp $\times$ cm are placed with their axes in the same vertical lines with similar poles facing each other. Each magnet has length of 1 cm. When the separation between the nearer poles is 1 cm. The weight of the.upper .magnet is supported by the repulsive force between the magnets. If g is 1000 $cm/sec^2$ the mass of the upper magnet is:

• A. 100g
• B. 45g
• C. 77.5g
• D. 55g

Answer 1

Answer: (D)

55g

Answer 2

In equilibrium position net repulsion due to magnetic interaction = weight of the upper megnet $\frac{900 \times 100}{1^2} + \frac{(-900) \times (-100)}{3^2} + \frac{900(-100)}{2^2} + \frac{(-900) 100}{2^2} + = m \times 1000 \, m = 55 \, g$