Question

You are moving into an apartment and take the elevator to the 6th floor. Suppose your weight is 790 N and that of your belongings is 960 N. (a) Determine the work done by the elevator in lifting you and your belongings up to the 6th floor (15.2 m) at a constant velocity. (b) How much work does the elevator do on you alone (without belongings) on the downward trip, which is also made at a constant velocity?

Answer 1

Answer:

a) $W=26600J$

b) $W=-12008J$

Explanation:

Given the information from the exercise we can calculate the work done by the elevator using the following formula:

$W=F*s$

a) Considering you and your belongings as a system we know that the elevator is applying a Normal reaction force of:

$F=790N+960N=1750N$

Since the force applied and the displacement is in the same direction, the work done by the elevator is positive

$W=(1750N)(15.2m)=26600J$

b) The reaction force applied by the elevator is the same as the weight of the person

$F=790N$

Since the force applied and the displacement is in opposite direction, the work done by the elevator is negative

$W=-(790N)(15.2m)=-12008J$