# Lifting an elephant with a pulley & rope

• Lamont
In summary: There would be some strapping around the elephant. A large pulley block (many pulleys) immediately above the elephant would hook to the strapping. Numerous turns of rope connect that block to a similar block 15m higher. The other end of the rope goes from top pulley block to workers. Why would the elephant not lift when the workers pull?If we use Sig Figs the answer because 4700 m regardless so I'll guess go with that.In summary, an elephant would require 5 km of rope to be lifted if the efficiency is 60%.
Lamont

## Homework Statement

Ringling Brothers Bamum and Bailey Circus is using a pulley to lift an Elephant on to a ship. If the Elephant is 2200kg and you have to raise her 15m with a pulley that has an efficiency of 60%, then how much rope do the handlers, who can pull with a combined force of 115 N, hope is available to them.

## Homework Equations

The force due to gravity on the elephant is 21,506 N (2200kg*9.8m/s^2)=F_e
15m=d
The force of the combined humans is 115N=F_p

Work W=F*d

## The Attempt at a Solution

The work needed to raise an 2200kg elephant 15 meters is 323,400 J
W=21,560 * 15=323,400 J
Since the efficiency is 60% the output and the work done to lift the elephant is the output, I divided 323,400 by 0.6 to get 539,000 J for the input.
I then divided by the force the combined handlers make up which is 115 N and got
4,687 m for the distance which mean the rope has to be more than 4,687 meters + at least 15m needed on the elephants side.
So would a rope greater than 4702 be the right answer?

Lamont said:

## The Attempt at a Solution

The work needed to raise an 2200kg elephant 15 meters is 323,400 J
W=21,560 * 15=323,400 J
Since the efficiency is 60% the output and the work done to lift the elephant is the output, I divided 323,400 by 0.6 to get 539,000 J for the input.
I then divided by the force the combined handlers make up which is 115 N and got
4,687 m for the distance which mean the rope has to be more than 4,687 meters + at least 15m needed on the elephants side.
So would a rope greater than 4702 be the right answer?

Almost 5 km of rope strong enough to hold the elephant would weigh more than the elephant.

Your calculation looks ok, except I don't understand the extra 15m. There may be a bit extra on the workers' side, but doesn't need to be 15m.
SteamKing said:
Almost 5 km of rope strong enough to hold the elephant would weigh more than the elephant.
Surely the tension in the rope is the 115N. The only parts that have to take the full weight are the pulley blocks and hooks at top and bottom. Even then, the rope's weight would be significant.

This question feels weird to me. I don't know how you could get a better answer than what you have, however:
115N*4687m = the amount of energy an applied force of 115N imparts to an object over the course of 4687 meters.

There is still a net force issue between the rope and the elephant. I can't see why the elephant should lift. Asking how many pullies would be necessary would be a better question in my opinion. As this is apparently your homework question, I am somewhat at a loss.

Any mechanics experts around?

haruspex said:
Your calculation looks ok, except I don't understand the extra 15m. There may be a bit extra on the workers' side, but doesn't need to be 15m.

Surely the tension in the rope is the 115N. The only parts that have to take the full weight are the pulley blocks and hooks at top and bottom. Even then, the rope's weight would be significant.

If we use Sig Figs the answer because 4700 m regardless so I'll guess go with that.

BiGyElLoWhAt said:
I can't see why the elephant should lift.
There would be some strapping around the elephant. A large pulley block (many pulleys) immediately above the elephant would hook to the strapping. Numerous turns of rope connect that block to a similar block 15m higher. The other end of the rope goes from top pulley block to workers. Why would the elephant not lift when the workers pull?

I gotcha, I was thinking 1 pully.

Another way is to convert 2200kgf to 21,575N and divide by 115N to get a 188X multiplier divided by the 0.6 efficiency to get 313X. Then 15m times 313X = 4700m of rope needed.

## 1. How is it possible to lift an elephant with a pulley and rope?

While it may seem impossible, it is actually achievable with the use of a complex system of pulleys. By using multiple pulleys and a rope, the force required to lift the elephant is spread out over a larger area, making it easier to lift the weight.

## 2. How many pulleys are needed to lift an elephant?

The number of pulleys needed depends on the weight of the elephant and the desired amount of force needed to lift it. Generally, the more pulleys used, the easier it will be to lift the elephant. However, a minimum of 4-5 pulleys is usually required for an average-sized elephant.

## 3. What is the weight limit for lifting an elephant with a pulley and rope?

The weight limit for lifting an elephant with a pulley and rope is dependent on the strength of the rope and the pulleys being used. The rope must be strong enough to handle the weight of the elephant, and the pulleys must be able to withstand the force required to lift the weight.

## 4. What are the potential risks involved in lifting an elephant with a pulley and rope?

There are several potential risks involved in attempting to lift an elephant with a pulley and rope. These include the risk of the rope breaking or the pulleys malfunctioning, which could result in the elephant falling and getting injured. It is important to carefully plan and execute the lifting process to minimize these risks.

## 5. Are there any other methods for lifting an elephant besides using a pulley and rope?

Yes, there are other methods for lifting an elephant, such as using cranes or other heavy machinery. However, these methods may be more expensive and less practical than using a pulley and rope system. Additionally, using a pulley and rope allows for more control and precision in the lifting process.

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