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calculusxy
 one year ago
MEDAL!!!
How much work is done by an elevator that carries a person with a mass of 70 kg up 40 meters? Assume the elevator has a constant acceleration of 2 m/s^2.
calculusxy
 one year ago
MEDAL!!! How much work is done by an elevator that carries a person with a mass of 70 kg up 40 meters? Assume the elevator has a constant acceleration of 2 m/s^2.

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Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1The elevator is not a inertial system, nevertheless, we can consider it, as an inertial system if we introduce the fictitious force m*Ac where Ac is the ecceleration of the elevator, and m is the mass of the person inside the elevator. So the situation is like below: dw:1437833008631:dw

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1in other word, on the person are acting two forces: the weight force whose magnitude is m*g= 70*9.81=...newtons the fictitious force, whose magnitude is m*Ac=70*2=...newtons Since the elevator is a inertial system, the laws of physics apply unchanged in it, so the requested work is: \[\Large W = m\left( {g + {A_c}} \right)h = ...joules\] where h=40 meters

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0So we are learning about energy now and the formulas that we have gone through so far are: Power = w/t Work = f x d Potential Energy: mass x gravity x distance Kinetic Energy: 1/2mv^2

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0The teacher said that he incorporated these formulas into the questions, so i need to understand what formulas go to what question to get the answer.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1you can apply this formula: Work = f x d providing that the force f is: f= m(Ac+g) where Ac=2 m/sec^2

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0Why can't we use the formulas to find the power because that this the amount of work done in an interval?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1the elevator is not an inertial system, since there are 2 forces acting on the person inside the elevator. I think it is better if we use the formula: work = force * distance

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0I still don't understand how you find the force.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1In other words, I have applied the Principle of Equivalence, and I consider the elevator like an inertial system, providing that to introduce the fictitious force

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0i am sorry , but i don't know the principle of equivalence because i am just a rising eighth grader.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1when you use an elevator in order to go up, at the starting of motion, you feel like pressed towards the floor of the elevator, right?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1that is due to the fictitious force which is acting on you

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1that fictitious force will add to your weight force

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0can we use the formula f = m x a?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1so the total force which is acting on you is: fictitious force+weight force

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1and the work done by the elevator is the work done by that total force

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0\[Force = mass \times acceleration\] \[Force = 70 kg \times 2m/s^2\] \[Force = 140 N \] Work: \[Force \times Distance \] \[140N \times 40 m\] \[1600J\]

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1yes! the fictitious force is given by the subsequent formula: f=m*Ac where Ac=2 m/sec^2

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1now you have to add the work done by the weight force

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0Oh... i am sorry about misinterpreting it because i didn't know that Ac actually meant acceleration.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1the work done by the weight force is: 70*9.8*40=...?

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0that's the potential energy right?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1the work done against the weight force is equal to the potential energy gained by the elevator

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0And now I have to add it: 27440 + 1600 = 29040

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1hint: 70*2*40=5600

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0i got lost after finding the force.

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1so, we have: 27440+5600=...

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0but why did we need to do 70*2*40?

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1the work done by the fictitious force, is : m*Ac*h= 70*2*40=...

Michele_Laino
 one year ago
Best ResponseYou've already chosen the best response.1\[{\text{work = force }} \times {\text{ distance = }}\left( {{\text{m}} \times {{\text{A}}_{\text{c}}}} \right) \times {\text{h}}\]

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0give me a minute...

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0so i do 27440 +5600= 33040

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0so that's my answer right?

calculusxy
 one year ago
Best ResponseYou've already chosen the best response.0thank you!!! i have another question may i ask that as well?
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