Physics
Physics
Problem
A lift is descending with a constant acceleration of . A passenger of mass stands on a spring balance kept on the lift floor. Take . a. (i) Calculate the reading shown by the spring balance while the lift is accelerating downward. b. (ii) If the supporting cable of the lift suddenly snaps so that the lift falls freely, determine the reading on the balance during the free fall.Intuitive explanation
The key is recognizing that the scale reads the normal force the floor exerts on the passenger, not their true weight. When the lift accelerates downward, the passenger needs a net downward force, so the normal force must be less than —use Newton's second law in the lift's reference frame to find it. The scale reading tells you how hard the floor is pushing up, which directly reveals the passenger's apparent weight.
Intuitive explanation
The key is recognizing that the scale reads the normal force the floor exerts on the passenger, not their true weight. When the lift accelerates downward, the passenger needs a net downward force, so the normal force must be less than —use Newton's second law in the lift's reference frame to find it. The scale reading tells you how hard the floor is pushing up, which directly reveals the passenger's apparent weight.