# How to stop a free-falling elevator

• bfosler
In summary, the conversation discusses a unique elevator problem where the cables break and the elevator begins to free-fall. The max allowed deceleration is 4m/s^2 and there is a small distance between the elevator and the walls. The coefficient between steel members and the elevator shaft is 0.3 and options for stopping the elevator are discussed. The suggestion of flooding the bottom of the shaft is mentioned as a potential solution.
bfosler
This is a different take on an elevator problem:

An elevator and contents have a mass of 300kg and travels at 2.5 m/s during normal operation. The elevator's cables break and begins to free-fall.

You need to stop the elevator and the max allowed deceleration is 4m/s^2. There is 0.05m between each side of the elevator and the walls, and the coefficient between steel members and the elevator shaft is mu(k)=0.3.

I assume that you can use steel wedges to help stop the elevator and then couple it with a spring mechanism at the bottom. But, it seems that even with 4 steel wedges on each side, the spring will need to create a force of ~500N.

Any suggestions...because I'm kinda all out of ideas

Thanks

It all depends on "when" you can apply your options. Is it immediately, or some?what? time before you can apply your options.

I would flood the bottom of the shaft myself. If you can get 10' of water, then you may only have a few broken legs.

for presenting this unique problem! As a scientist, my first suggestion would be to consider alternative solutions to stopping the elevator. While using steel wedges and a spring mechanism may work, it may also be a complex and time-consuming process.

One possible solution is to use a magnetic braking system. This involves installing powerful electromagnets on the walls of the elevator shaft. When the elevator falls, these magnets would create a magnetic field that would interact with the metal components of the elevator, generating a force that opposes the direction of motion, thus slowing down the elevator. This method has been used in high-speed trains and roller coasters and could be adapted for use in an elevator.

Another option to consider is using a parachute system. This would involve deploying a parachute from the top of the elevator shaft when the cables break. The parachute would create air resistance and slow down the elevator's descent. This method may also require less force from the spring mechanism, as the parachute would do most of the work in slowing down the elevator.

Additionally, implementing an emergency brake system in the elevator could also be a viable solution. This would involve installing a brake mechanism that can be activated in the event of an emergency. The brake could be designed to engage automatically when the elevator reaches a certain speed, thus slowing it down and bringing it to a stop.

Ultimately, the best solution will depend on various factors such as cost, feasibility, and safety. It may be beneficial to consult with engineers and experts in elevator technology to determine the most effective solution for this specific situation.

## 1. How does an elevator free-fall?

An elevator free-falls when the cables that support it are suddenly cut or malfunction, causing the elevator car to drop at a high speed due to the force of gravity.

## 2. Can an elevator free-fall be stopped?

Yes, it is possible to stop a free-falling elevator by using a safety system called an emergency brake. This brake is activated when the elevator exceeds a certain speed, and it brings the car to a stop by gripping onto the elevator shaft.

## 3. How long does it take for an elevator to free-fall?

The duration of a free-fall depends on the height of the building and the speed at which the elevator car is falling. However, in most cases, the elevator will reach the bottom of the shaft in less than 10 seconds.

## 4. What safety measures are in place to prevent an elevator from free-falling?

Elevators are equipped with multiple safety features to prevent a free-fall, such as the emergency brake mentioned earlier, as well as overspeed governors and counterweights. Regular maintenance and inspections are also necessary to ensure these safety systems are functioning properly.

## 5. What should I do if I am in an elevator that is free-falling?

If you find yourself in a free-falling elevator, stay calm and do not panic. Press the emergency button or use the alarm to alert someone for help. You can also try to jump right before the elevator reaches the ground, as this can help reduce the impact of the fall. However, it is important to follow the instructions of the elevator manufacturer or building staff in case of an emergency.

• Introductory Physics Homework Help
Replies
5
Views
1K
• Introductory Physics Homework Help
Replies
5
Views
3K
• Mechanics
Replies
25
Views
3K
• Introductory Physics Homework Help
Replies
4
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
3K
• Introductory Physics Homework Help
Replies
4
Views
10K
• Introductory Physics Homework Help
Replies
15
Views
30K
• Introductory Physics Homework Help
Replies
5
Views
4K
• Other Physics Topics
Replies
6
Views
2K
• Other Physics Topics
Replies
6
Views
2K