A suspension bridge oscillates with an effective force constant of 1.2.108 (a) How much energy is needed to make it oscillate with an amplitude of 0.2 m? PE el= J (b) If soldiers march across the bridge with a cadence equal to the bridge's natural frequency and impart 1.1.104 J of energy each second, how long does it take for the bridge's oscillations to go from 0.2 m to 0.55 m amplitude? t= - Think and Prepare: 1. What is the change in energy of the oscillator at the two amplitudes? 2. At what rate is energy added to the bridge? From the rate of energy transferred, how can you determine the time over which the transfer takes place? S m

A suspension bridge oscillates with an effective force constant of 1.2.108 (a) How much energy is needed to make it oscillate with an amplitude of 0.2 m? PE el= J (b) If soldiers march across the bridge with a cadence equal to the bridge's natural frequency and impart 1.1.104 J of energy each second, how long does it take for the bridge's oscillations to go from 0.2 m to 0.55 m amplitude? t= - Think and Prepare: 1. What is the change in energy of the oscillator at the two amplitudes? 2. At what rate is energy added to the bridge? From the rate of energy transferred, how can you determine the time over which the transfer takes place? S m