Weight of a person in a elevator going down

In summary, the problem involves a passenger with a mass of 72.2kg standing on a weight scale in an elevator. The elevator is descending with a constant acceleration of 3.20 m/s^2 and the question is what the reading on the scale would be. If the elevator had a constant acceleration of 9.8m/s^2, the scale would read -938.6n. This shows that the effective acceleration on the passenger is affected by the acceleration of the elevator. The normal force on the passenger also changes, causing a change in the reading on the scale. The weight of the person is 708.282 and the upward lift on the person is 231.04, resulting in a net 'weight
  • #1
stealthcataf
2
0
Im new to physics and I am trying to do some problems here, I hope someone can help me, here it goes :

If a passenger with a mass of 72.2kg stands on a weight scale in a elevator. What is the reading on the scale if the elevator goes down with a constant acceleration of 3.20 m/s^2.
 
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  • #2
If the elevator was descending at constant acceleration of 9.8m/s^2, what would the scale read? Why?

What does this tell you about the effective acceleration on the passenger?
 
  • #3
Ive done some calcs, correct me if I am wrong

m=72.2kg
a=-3.20 m/s^2

SumFx=0
SumFy=Fn-mg=ma

ma=72.2(-3.20)=-231.04n

Fn=mg+ma=72.2(-9.8)+72.2(-3.20)=-938.6n
Is this the apparent weight?
 
  • #4
If the elevator is going down, then is he pressing MORE on the scale or less?
It is the normal force that gives the reading on the scale. How is the normal force affected when the elevator is falling?
 
  • #5
Weight of person=72.2*9.81=708.282
upward lift on person=72.2*3.2=231.04
Therefore net 'weight' of person=708.282-231.04=477.242
 

1. How does the weight of a person in an elevator change when it is going down?

When an elevator is going down, the weight of a person will appear to decrease. This is because the elevator is accelerating downwards and the force of gravity is pulling the person towards the ground. This creates a smaller normal force, which is what we perceive as weight.

2. Does the weight change for different people in the elevator?

No, the weight of a person in an elevator going down will remain the same regardless of their size or weight. This is because the force of gravity acts on all objects equally, regardless of their mass.

3. Why do we feel lighter in an elevator going down?

We feel lighter in an elevator going down because the elevator is accelerating downwards, creating a smaller normal force and thus making us feel like we weigh less. However, our actual weight does not change.

4. Can the weight of a person in an elevator going down ever be negative?

No, the weight of a person in an elevator going down can never be negative. Weight is a measurement of the force of gravity acting on an object, and gravity can only pull in one direction - towards the ground. Therefore, weight can only be positive or zero, but never negative.

5. Does the weight change if the elevator is going down at a constant speed?

No, the weight of a person in an elevator going down at a constant speed will remain the same. This is because there is no acceleration, so the normal force and weight will be equal. However, the person may still feel lighter due to the sensation of downward movement.

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