In an electricity experiment, a 1.0g plastic ball is suspended on a60-cm-long string and given an electric charge. A charged rodbrought near the ball exerts a horizontal electrical forceFelec on it, causing the ball to swing out to a 20deg. angle and remain there.

a. What is the magnitude of Felec ?
b. What is the tension in the string?

The tension in the string is due to the electric force, and the weight of the ball.

The correct responses are;

a. The magnitude of is approximately 3.57 × 10⁻³ N

b. The tension in the string is approximately 1.044 × 10⁻² N

Reasons:

The given  parameters are;

Mass of the plastic ball = 1.0 g

Length of the string from which the ball is suspended = 60 cm

Angle of swing of the ball, θ = 20°

a. The magnitude of the electric force, is given as follows;

= T×sin(20°)

W = T×cos(20°)

Where;

T = Tension in the string

W = The weight of the ball = 1.0 g × 9.81 m/s² = 0.00981 N

= W × tan(20°)

∴ = 0.0098 N × tan(20°) ≈ 0.00357 N

The magnitude of ≈ 0.00357 N = 3.57 × 10⁻³ N

b. The tension in the string is found from W = T×cos(θ)

The tension in the string ≈ 0.01044 N = 1.044 × 10⁻² N

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