Two charged balls are connected by an inextensible thread of length 3 m. Masses of balls are 2 kg and 1 kg, the charges are +20 μC and −100 μC. What minimum constant external force F (in N) must be applied to the ball of mass 1 kg so that the thread does not slack? Neglect gravity and friction.
Physics · Electrostatic
JEE Mains Advanced

Question

Two charged balls are connected by an inextensible thread of length 3 m. Masses of balls are 2 kg and 1 kg, the charges are +20 μC and −100 μC. What minimum constant external force F (in N) must be applied to the ball of mass 1 kg so that the thread does not slack? Neglect gravity and friction.

Physics · Electrostatic

G1 Physics · Accepted Answer

Step 1: Identify the relevant electrostatic principle—Coulomb's law, superposition, Gauss's law, potential-energy conservation or conductor boundary conditions. Step 2: Write the corresponding equation using the quantities in the question and simplify the geometry. Step 3: Substitute the given values and compare with the alternatives. Final: 3. In this specific setup, apply the calculation to: Two charged balls are connected by an inextensible thread of length 3 m. Masses of balls are 2 kg and…