A simple pendulum bob of mass 20 g has total mechanical energy (kinetic plus potential) 0.02 J. Find the approximate speed when it passes through its equilibrium position.
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Question

A simple pendulum bob of mass 20 g has total mechanical energy (kinetic plus potential) 0.02 J. Find the approximate speed when it passes through its equilibrium position.

G1 Physics · Accepted Answer

Step 1: At the lowest/equilibrium position, choose gravitational potential energy to be zero and kinetic energy to be maximum. Step 2: Total mechanical energy E = ½mv(max)². Step 3: Given E = 0.02 J and m = 20 g = 0.020 kg. Step 4: v(max)² = 2E/m = (2 × 0.02)/0.020 = 2 m²·s⁻². Step 5: v(max) = √2 ≈ 1.414 m·s⁻¹. Final answer: √2 m·s⁻¹ (Option D).