Question

When a 45-kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true?

Answer 1

The elevator is accelerating upwards at
`0.87m/s^(2)`.

Step-by-step explanation:

Weight is a force and is measured in newtons (N). Measuring weight in kg is a mistake as kg is a unit of mass (not weight). On the surface of the planet, due to gravity, 1kg of mass produces a force of 9.8 newtons. Therefore, 45kg should produce
`45kg * 9.8 m/s^(2)=441 N`. There is an extra
`480N - 441N=39N`. Given that
`1N=1kg * 1m/s^(2)`, we have
`(1N)/(1kg)=1m/s^(2)`.

So, we need to calculate the acceleration related to these extra 39N:
`(39N)/(45kg)=0.87m/s^(2)`

Answer 2

The elevator is accelerating upwards.

Step-by-step explanation:

The scale should read the weight of the person, which is approximately 450N. Since the scale reads a higher value, the elevator must accelerate upwards to increase the normal force on the scale.