Question

Five balls numbered $1$ to $5$ are suspended using separate threads. Pairs $(1,2),(2,4),(4,1)$ show electrostatic attraction while pairs $(2,3),(4,5)$ show repulsion. There ball $1$ must be

• A. positively charged
• B. negatively charged
• C. neutral
• D. made of metal

Answer 1

Answer: (C), (D)

The correct options are
C neutral
D made of metal

Ball 2 is positively charged then ball 4 s negatively charged because 2 and 4 show attraction. Now, if ball 2 is positively charged then ball 3 is also positively charged because 2 and 3 show repulsion and similarly, ball 5 is negatively charged since 4 and 5 show repulsion. And now, we are left with ball 1 and it can never be positively charged because ball 2 and 1 show attraction, it means ball 1 s negatively charged but it is also not possible because ball 1 and 4 also show attraction. So, ball 1 is neither positively nor negatively charged. It means ball 1 is neutral and made of metal.