Chapter 4 Problem 70

From 105/106 Lecture Notes by OBM

Problem

A 75.0-kg person stands on a scale in an elevator. What does the scale read (in N and in kg) when

(a) the elevator is at rest,

(b) the elevator is climbing at a constant speed of 3.0 m/s,

(c) the elevator is descending at 3.0 m/s,

(d) the elevator is accelerating upward at 3.0 m/s ,

(e) the elevator is accelerating downward at 3.0 m/s?

Solution

diagram

Newton’s second law for the person:

The scale always take acceleration as , thus

(a)

(b)

; ; ;

(c)

; ; ;

(d)

(e)