Question

a person of mass 90 kg stands on a scale in an elevator. the scale reads 1100 n. which of the following is a correct claim about the direction of the elevators motion?
a the elevator must be moving upward.
b the elevator could possibly be moving upward and slowing down.
c the elevator must be moving downward.
d the elevator could possibly be moving downward and slowing down.

Explanation:

Step1: Calculate the weight of the person

The weight of the person \(W = mg\), where \(m = 90\space kg\) and \(g= 10\space m/s^{2}\). So \(W=90\times10 = 900\space N\)

Step2: Analyze the net force and acceleration

The normal force \(N = 1100\space N\). Using Newton's second law \(F_{net}=N - W=ma\). Substituting the values, \(1100 - 900=90a\), so \(a=\frac{200}{90}\approx2.22\space m/s^{2}\) (upward acceleration).
When the acceleration is upward, the elevator can be either moving upward and speeding up or moving downward and slowing down.

Answer:

D. The elevator could possibly be moving downward and slowing down.