Question

A student weighing 500 N stands on a bathroom scale in the school’s elevator. When the scale reads 520N, the elevator must be 

(A) accelerating upward. 

(B) accelerating downward. 

(C) moving upward at a constant speed. 

(D) moving downward at a constant speed. 

(E) at rest

Answer 1

Correct option  (A) accelerating upward.

Elevator physics: F_N represents the scale reading. ΣF = ma; F_N – mg = ma, or F_N = m(g + a). When F_N > mg, the elevator is accelerating upward (a is positive).