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A sidecar is a kind of box with wheels which you can attach to the side of a motorcycle so that you can carry a passenger in it. (附于摩托车旁用于载人的)侧车
Take, for example, UM 006, the corpse she observes working with researchers at Wayne State University in Detroit to determine how much force a human shoulder can withstand in a side-impact car crash before it sustains serious injury.