Another Confusing physics hw....?

Question

An elevator has a mass of 1170kg and carries a maximum load of 739kg. A constant frictional force of 3220N retards its motion upward. The acceleration of gravity is 9.8m/s^2

1. What must be the minimum power delivered by the motor to lift the elevator at a constant speed of 2.91m/s? Answer in units of W

2. What power must the motor deliver at an instantaneous speed of 2.91m/s if the elevator is designed to provide an upward acceleration of 1.37m/s^2? Answer in units of W

Answer 1

First, compute the force on the cable pulling the elevator up:

for 1 it is
m*g * friction

for 2, you add in the additional force of acceleration:

m*g + friction + acceleration*g

For power, compute the instantaneous power as

p=force*velocity

j

Answer 2

nicely what you opt to think of approximately is not any remember if or no longer there is a few non-conservative rigidity appearing on the article. Like selection a million isn't keeping momentum using fact there is an exterior rigidity being utilized (the breaking rigidity thus). 2. particular. Frictionless so no non-conservative exterior forces. 3. i think of you are able to argue particular. If pi = pf (m1v1i + m2v2i) = (m1v1f + m2v2f) Mass one is virtually negligible while in comparison with a great wall. And vi and vf for wall = 0 (m1v1 + 0) = (m1v1f + m2v2f) So i think technically particular using fact no exterior non conservative forces, in spite of the indisputable fact that i think of its arbitrary and you are able to argue the two way. yet i might placed particular