試題詳解

12.A block with mass m 250g is fastened to a spring with spring constant k 85N/m. The system is excited to oscillate. Assume that there is a velocity-dependent damping force F_d -bv in the system with b 70g/s. How long does it take for the amplitude of the damped oscillation to drop to half its initial value? (ln2 0.693)
(A)3s
(B)4s
(C)5s
(D)6s
(E)7s