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?

a)

b)

Explanation:

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

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

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

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

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

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explanation:

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s