Elevator Problem: Find Scale Reading in Falling Elevator

  • Thread starter Toxage
  • Start date
  • Tags
    Elevator
In summary, when a 80.0 kg person stands on a scale in an elevator that is falling at a constant speed of 3.5 m/s, the scale will read their weight of 882 Newtons. However, when the elevator is accelerating, the formula Fnet = m(a + g) must be used, taking into account the direction of acceleration.
  • #1
Toxage
17
0

Homework Statement



A 80.0 kg person stands on a scale in an elevator.
(c) What does it read when the elevator is falling at 3.5 m/s?

Homework Equations



EF = MA

The Attempt at a Solution



I can't even attempt the solution because I don't know acceleration...
 
Physics news on Phys.org
  • #2
Toxage said:
A 80.0 kg person stands on a scale in an elevator.
(c) What does it read when the elevator is falling at 3.5 m/s?

I can't even attempt the solution because I don't know acceleration...

Hi Toxage! :smile:

If the speed is constant, then the acceleration is … ? :wink:
 
  • #3
tiny-tim said:
Hi Toxage! :smile:

If the speed is constant, then the acceleration is … ? :wink:

Then the acceleration is equal to 0.

EF = MA

EF = M(0)

EF = 0

Fn - Fg = 0

Fn = Fg

80(9.8) = 882 Newtons

882/9.8 = 80kg

Doesn't work... Webassign says its the wrong answer...


Did I do something wrong in my math?
 
  • #4
No your maths looks fine. What is the quoted answer? If your standing on scales and not accelerating the scales will tell you your weight. When you are accelerating use this formula:

[tex] F_{net} = m(a + g) [/tex]

But MAKE SURE YOU DEFINE A POSITIVE DIRECTION AND STICK TO IT. So if you define up as positive, g = -9.81. And then when accelerating up, a is positive and vice versa.
 

FAQ: Elevator Problem: Find Scale Reading in Falling Elevator

What is the purpose of solving the "Elevator Problem"?

The "Elevator Problem" is used to calculate the scale reading of a person standing on a scale inside a falling elevator. This can help determine the actual weight of the person and the impact of gravity on the scale reading.

How does gravity affect the scale reading in a falling elevator?

Gravity has a major impact on the scale reading in a falling elevator. As the elevator falls, the acceleration due to gravity increases, making the scale reading appear higher than the actual weight of the person.

What factors affect the scale reading in a falling elevator?

The two main factors that affect the scale reading in a falling elevator are the acceleration due to gravity and the initial velocity of the elevator. Other factors such as air resistance and the mass of the elevator can also play a role.

Can the "Elevator Problem" be solved using only Newton's laws of motion?

Yes, the "Elevator Problem" can be solved using only Newton's laws of motion. By applying the laws of motion to the falling elevator, we can calculate the acceleration and use it to determine the scale reading.

How is the scale reading affected if the elevator is moving at a constant velocity?

If the elevator is moving at a constant velocity, the scale reading will remain the same as the actual weight of the person. This is because there is no acceleration, and therefore, no change in the force exerted on the person by the scale.

Similar threads

Back
Top