A 514-N physics student stands on a bathroom scale in an 820-kg (including the s

Question

A 514-N physics student stands on a bathroom scale in an 820-kg (including the student) elevator that is supported by a cable. As the elevator starts moving, the scale reads 480 N .
Part A
Find the magnitude of the acceleration of the elevator.

a =
  m/s2  

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Part B
Find the direction of the acceleration of the elevator.

Find the direction of the acceleration of the elevator.

upwards
downwards

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Correct
Part C
What is the acceleration if the scale reads 629 N ?

a =
  m/s2  

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Part D
If the scale reads zero, should the student worry? Explain.
Essay answers are limited to about 500 words (3800 characters maximum, including spaces).
3800 Character(s) remaining
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Part E
What is the tension in the cable in part A?

T =
  N  

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Part F
What is the tension in the cable in part D?

T =
  N  

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Explanation / Answer

In downward motion of elevator reading of scale decrease so reading is

N = mg - ma

given mg = 514N

m = 514/g = 514/9.8= 52.44kg

N= 480N

acceleration

a = 0.65m/s^2

Part B

direction is downward

Part C

if scale reads 629N , lift is moving upwards

N = mg+ma

a = 2.2m/s^2

Part D

If reading of scale is zero then

mg = ma

so acceleration is equal to gravitational acceleration means this is a free fall. in free fall acceleration is equal to gravitational acceleration. this can happen because of breaking of cables supporting the elevator so this is a case of worry for student

Part E

tension in cable in part A

Mg-T = Ma

T = 820*9.8-820*0.65

T = 7503N

Part F

In part D there is a free fall so tension in the cable is zero

T = 0

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