When you walk with a backpack, do y

When you walk with a backpack, do you know how the things insidemove from side to side? Now scientists have figured out how to tap into that movement to produce electricity.Picture a pendulum (摆锤) fixed to a backpack frame and stabilized with springs on either side. The pack' s weight is attached to the pendulum, so the pendulum swings side to side as you walk. Then' a machine is driven by that swinging movement, and spits out electrical current to charge a battery.Volunteers carried the pack while walking on a running machine and wore masks to measure the flow of O2 and CO2. Walking with theslightly swinging 20-pound load, the device (设备) did not significantly affect the volunteers' metabolic (新陈rate代谢的)compared to when they. carried thesame weightfixed. in place. In- fact, the energy-harvesting packreducedtheforcesof acceleration they' d feel in a regular pack, which might mean greater comfort for a long hike. And the devicedid produce a steady trickle (涓 流). of electricity. If you up the load to 45 pounds, the swing of the pack could fully charge a smartphone only'