Question

You are moving into an apartment and take the elevator to the 6th floor. Suppose your weight is 660 N and that of your belongings is 1100 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:

Explanation:

Total weight

My weight+weight of belongings

660+1100=1760N.

a. Work done by the elevator to travel a total height of 15.2m

Using newton law of motion

ΣF = ma

There are only two forces acting upward, the weight and the reaction by the elevator

Also note it is moving at constant velocity then, a=0

N - W=0

Then, N=W

N=1760N

So, workdone is given as

Wordone, =force × distance

Work done=1760×15.2

W=26,752J

W=26.752KJ

b. Work done on me alone is still need to go through the same process but will remove the weight of the belonging

Therefore,

Weight now = 660N

And using the same equation of motion

ΣF = ma

Comstant velocity, a=0

N - W=0

N=W

N=660N

Then, workdone

W=F×d

W=660×15.2

W=10,032J

W=10.032KJ

Answer 2

Answer:

A, 26752J

B, -10032J

Explanation:

See attachment below

Since the elevator is moving at a constant speed, we can then say

F(elev)=W(total)

While going up, the displacement is pointing upwards

W(up) = F*S = F*S cos0° = F*S

Since forces F and S point in the same direction, the angle in between them, thus is zero. We also know, F(elev) is the upward weight. Thus

W(up) = F*S = W(total)*S =

= (660N+1100N)*15.2m

= 1760N * 15.2m

= 26752J

While going downwards, the displacement S is pointing down and the weight going down is just the person, so we have

W(down) = F*S = F*S cos180° = -F*S

W(down) = -F*S = -W(total)*S

= -660 * 15.2

= - 10032J

Thus,