Physics
Physics
Problem
A student stands on a bathroom scale while riding in a roller-coaster car that travels through a vertical circular loop of radius . As the car passes the lowest point of the loop, the scale reading is noticeably larger than the student’s true weight. Which of the following best explains the increased reading? a) At the bottom, both gravity and the required centripetal force act downward, so the scale must exert a normal force large enough to oppose their combined effect, leading to a higher reading. b) At the bottom, a radially outward “centrifugal” force pushes the student against the scale in addition to gravity, so the scale reading becomes larger. c) At the bottom, the net force toward the center of the loop must exceed the gravitational force, so the scale must supply an additional upward force, increasing the normal force it exerts. d) Because the student’s kinetic energy is greatest at the bottom, conservation of energy requires the normal force to be largest there, which shows up as an increased scale reading.Intuitive explanation
At the lowest point of the loop, the student is accelerating upward toward the center of the circular path. The scale must push up hard enough not only to support the student's weight, but also to provide the extra net force needed for that centripetal acceleration. This is why the normal force—what the scale reads—exceeds . Think of it as the scale working overtime to both hold you up and curve your path.
Intuitive explanation
At the lowest point of the loop, the student is accelerating upward toward the center of the circular path. The scale must push up hard enough not only to support the student's weight, but also to provide the extra net force needed for that centripetal acceleration. This is why the normal force—what the scale reads—exceeds . Think of it as the scale working overtime to both hold you up and curve your path.