A 3 kg block is attached to a spring (k=200 N/m) and moves at 4 m/s. What is its kinetic energy when the spring is compressed 20 cm?
Correct: A
Energy conservation: initial KE + initial PE = final KE + final PE. ½×3×4² + 0 = KE + ½×200×0.2² ⇒ 24 = KE + 4 → KE = 20 J. Answer not listed; possible error in choice.