11.2 Example 2

A block of 4 kilograms of mass is above a scales inside an elevator with an acceleration of 1.6 m/s2 to the upwards. Which is the weight that show the scales?

Solution with FisicaLab

Erase the content of the chalkboard and select the SI system. And add one element Force, one element Block with vertical movement and one element Stationary reference system, to make the free body diagram of the block. As show the image below:

We don’t have a time data, but we can assume anytime. Here we assume 1 second. Also, we don’t have an initial velocity data, we will assume 0. Then to the element Stationary reference system write:

g

9.81

t

1

The searched wight is the same if we assume other time or initial velocity. To the element Block with vertical movement write:

Name

Block

m

4

a

1.6

vi

0

vf

vf

d

d

Relative to

sf

To the element Force, that is the normal force and the searched weight, write:

f

n

Now click in the icon Solve to get the answer:

n = 45.640 N ;  vf = 1.600 m/s ;  d = 0.800 m ;
Status = success.

The relevant data is n = 45.640 N.