Question

A 75.0-kg person stands on a scale in an elevator. What does the scale read (in N) when the elevator is at rest? What does the scale read (in N) when the elevator is climbing at a constant speed of 3.0 m/s? What does the scale read (in N) when the elevator is descending at 3.0 m/s? What does the scale read (in N) when the elevator is accelerating upward at 2.5 m/s2 ? What does the scale read (in N) when the elevator is accelerating downward at 2.5 m/s2 ?

Answer 1

on earth
at rest
75 kg * 9.8 m/s^2 = x Newtons

at constant speed, no acceleration, still the same 75*9.81

still at constant speed down, still the same

acc up = 2.5 m/s^2, now we are getting somewhere
net Force up on person = m * 2.5 m/s^2
weight force down on person = m g = m * 9.8
scale force up - m g = m a
scale force up = m (g+a) = 75 ( 9.8 + 2.5)
if a = -2.5 then
75 (9.8 - 2.5)

Answer 2

w=750N

Answer 3

Incorrect answer, Gravity is a downward force therefore it is -9.8 or -9.81. You do -9.81-2.5 and then multiply it out.