Asked by Physics
When I asked my teacher for help he told me this
This is a logical puzzle. Having 75% of the typical weight means experiencing 75% of the typical gravity. The floor must be falling away with an acceleration of 25% of typical gravity.
Here's the question I asked that's from my textbook
A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only .75 of the person''s regular weight. Calculate the acceleration of the elevator, and find the direction of acceleration.
ok isn't weight by defintion the force of gravity which is equal to mass time gravity how could this every change? I understand that in this situation the net force change but no the actual weight so I'm lost... I'm know the normal force exerted by the scale onto the person would change becasue the acceleration changes and for a brief moment weighs less than she would without going in the elevator...
so I'm the normal force exerted by the scale onto the person would obviously change but how would her weight change?
Can you explain to me how to do this problem or as to why I can do this problem this way because I do not understand it. Thanks
This is a logical puzzle. Having 75% of the typical weight means experiencing 75% of the typical gravity. The floor must be falling away with an acceleration of 25% of typical gravity.
Here's the question I asked that's from my textbook
A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only .75 of the person''s regular weight. Calculate the acceleration of the elevator, and find the direction of acceleration.
ok isn't weight by defintion the force of gravity which is equal to mass time gravity how could this every change? I understand that in this situation the net force change but no the actual weight so I'm lost... I'm know the normal force exerted by the scale onto the person would change becasue the acceleration changes and for a brief moment weighs less than she would without going in the elevator...
so I'm the normal force exerted by the scale onto the person would obviously change but how would her weight change?
Can you explain to me how to do this problem or as to why I can do this problem this way because I do not understand it. Thanks
Answers
Answered by
Count Iblis
Her weight doesn't change, but her so-called "apparent weight" does change:
http://en.wikipedia.org/wiki/Apparent_weight
http://en.wikipedia.org/wiki/Apparent_weight
Answered by
Marth
"how would her weight change?"
The force of weight we sense is actually the normal force, or the force pushing us up. If the elevator accelerates downward, that force is reduced, as is our perception of our weight.
By Newton's 3rd law, the sum of the forces acting on the person equals the mass times acceleration.
sum(F) = ma.
the sum of forces also equals the normal force + the force of weight.
sum(F) = Fn - Fw
When the person is at rest, the sum of the forces = 0.
0 = Fn - Fw
However, when the elevator accelerates downwards, the Fn is only .75 of what it was.
sum(F) = .75Fn + FW
ma = .75mg - mg
a = .75g - g
a = -.25g
The force of weight we sense is actually the normal force, or the force pushing us up. If the elevator accelerates downward, that force is reduced, as is our perception of our weight.
By Newton's 3rd law, the sum of the forces acting on the person equals the mass times acceleration.
sum(F) = ma.
the sum of forces also equals the normal force + the force of weight.
sum(F) = Fn - Fw
When the person is at rest, the sum of the forces = 0.
0 = Fn - Fw
However, when the elevator accelerates downwards, the Fn is only .75 of what it was.
sum(F) = .75Fn + FW
ma = .75mg - mg
a = .75g - g
a = -.25g
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.