Final answer:
A power rack is a mechanical spotter for free-weight training that provides safety and support during weightlifting exercises.
Step-by-step explanation:
A mechanical spotter for free-weight training is called a power rack or squat rack.
Power racks are designed to provide safety and support during weightlifting exercises. They consist of a metal frame with adjustable safety bars that can catch the barbell if the lifter fails to complete a repetition or needs assistance.
Using a power rack ensures that the weightlifter can challenge themselves with heavier weights without the risk of injury, as the safety bars act as a mechanical spotter.