Trying to solve an elevator problem

  • Thread starter Robertoalva
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    Elevator
In summary, the elevator exerts a force of 304.06 N on the passenger, with 156.86 N being the normal force and 147.2 N being the passenger's weight. The tension of the elevator cable is not needed in this calculation.
  • #1
Robertoalva
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Homework Statement


An elevator accelerates downward at 3.2 m/s2. What force does the floor of the elevator exert on a 46 kg passenger?


Homework Equations



T+F=ma
T being tension

The Attempt at a Solution


I don't know if the tension of the elevator line is 9.81N, and in the passenger I got 147.2 N for his force(using the acceleration of the elevator.
 
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  • #2
You don't need the tension of the elevator cable here since it doesn't directly act on the passenger.

Draw a free-body diagram for the passenger and use Newton 2.
 
  • #3
so i basically get the force of the person by, multiplying 49kg*3.2m/s^2 right? if so, then how do I get the force of the floor? it is less because the elevator is going down right?
 
  • #4
What are the 2 forces acting on the passenger?
Draw these on a diagram and add them.
Their sum will be the quantity you calculated.
( Make sure that your signs are correct here ).

You are right in saying that the normal force will get less.
 
  • #5
so, the answer would be 137.39N ? because of the substraction of the normal force of the man and the default force 9.81N?
 
  • #6
No.

The normal force on the passenger acts upwards, and the weight acts downwards.
The sum of these is the quantity you calculated in #3, ( from F(net) = ma ).

You can work out the normal force from this.
Choose one direction as positive ( eg the downward direction ) and make sure your signs are correct.
 
  • #7
so it would be 304.06 - 147.2 = 156.86N
 
  • #8
Where does the 304.06 come from?

You should have something like
mg - n = ma
 
  • #9
well, is (9.81-3.2)*46= 304.06 and that's the final answer.
 
  • #10
Yes :)
 

Related to Trying to solve an elevator problem

1. How do elevators calculate the weight of passengers?

Elevators typically use sensors located under the floor of the elevator car to measure the weight of passengers and adjust the speed and power of the elevator accordingly.

2. Why do elevators sometimes skip floors or stop at random floors?

This can be due to multiple factors such as the elevator being programmed to prioritize certain floors, heavy passenger traffic, or a malfunction in the elevator's sensors or control system.

3. What can cause an elevator to get stuck between floors?

Elevator malfunctions such as a power outage, mechanical failure, or faulty sensors can cause an elevator to get stuck between floors. Human error, such as overloading the elevator or pressing too many buttons, can also be a contributing factor.

4. How do elevators ensure passenger safety in case of an emergency?

Modern elevators are equipped with several safety features such as emergency stop buttons, backup power supplies, and emergency communication systems. In the event of an emergency, elevators are designed to automatically stop and open the doors closest to the nearest floor.

5. How can elevators be made more energy-efficient?

Elevators can be made more energy-efficient by implementing features such as regenerative drives, which capture and reuse energy generated during braking, or by using destination dispatch systems, which group passengers with similar destinations to reduce the number of stops and energy consumption.

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