How to Lift Extremely Heavy Weights

I have a 200 kg block on the floor, that I want to raise 2m vertically. Without doing myself some kind of lasting damage, how do I accomplish this task on my own ?

I am reasonably sure that I could lift a 50kg mass this far but no more .... can you come up with a design that will allow me to do this ?

When you have your answer, you may like to consider the work done in each of your design scenarios......

Solution

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Solution

You need to add a second and third pulley to the system to allow me to raise the mass. Here’s how it would look.... (and pretend that the Lbs are kgs!)

Graphic - Pulley Diagram

The pulley attached to the mass consists of 2 separate pulleys on the same shaft, halving the force (but doubling the distance I must pull the rope....) In fact, the diagram is slightly incorrect, as the tension in the two outside sections of the rope is not 25lbs, as the ropes are not vertical. The vertical component is in fact 25cosθ, but if θ is small it is a good approximation.

So, there is the trade-off.... I can exert a force equal to 1/4 of the weight of the object that allows me to just lift it, but I must pull it four times further. Hence the work done is the same whether I have superhuman strength or not....

This is the way a block and tackle works, used for (amongst other things) manually lifting car engines out of the body. It is also an example of a force-distance trade-off, which occurs in many other areas as well, such as levers.

Now let’s take a look at the real thing ....