Four identical particles, each of mass m and charge q, are placed at the vertices of a square of side ℓ. They are released simultaneously from rest on a frictionless plane. Select the correct statement(s).
Select all that apply

Question

Four identical particles, each of mass m and charge q, are placed at the vertices of a square of side ℓ. They are released simultaneously from rest on a frictionless plane. Select the correct statement(s).

Select all that apply

G1 Physics · Accepted Answer

Step 1: Symmetry is preserved: all four charges have identical radial acceleration away from the square centre, so the configuration remains a square; A is true. Step 2: When the side changes, conserve total electrostatic potential energy plus total kinetic energy. Initial U=kq²(4/ℓ+2/(√2ℓ)); evaluate U after the stated displacement. Step 3: The resulting speed is √{[q²/(8πε₀mℓ)](2+1/√2)}, so C is true. Final: A, C.