20. A transverse wave travels along a string according to the equation y(x,t) = 0.05 sin(0.4πx + 3πt + π/3). (x, y in meters, t in seconds). What is the speed of propagation of the wave, in m/s? (A) 1.2 (B) 4.0 (C) 7.5 (D) 9.0 (E) 12.0

6. Two far apart charged metal spheres of radius R₁ and R₂ are connected by a long wire in electrostatic equilibrium. The electric potentials and the surface charge densities on them are V₁, V₂ and σ₁, σ₂, respectively. Choose the correct statement. (A) V₁ ＞ V₂, σ₁ ＞ σ₂ (B) V₁ ＜ V₂, σ₁ ＜ σ₂ (C) (D) V₁ = V₂, R₁σ₁ = R₂σ₂ (E) R₁V₁ = R₂V₂, σ₁ = σ₂

20. A transverse wave travels along a string according to the equation y(x,t) = 0.05 sin(0.4πx + 3πt + π/3). (x, y in meters, t in seconds). What is the speed of propagation of the wave, in m/s?
(A) 1.2
(B) 4.0
(C) 7.5
(D) 9.0
(E) 12.0

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