(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A bucket of water is raised up out of

a well with a device of the rope, and

pulleys as shown in figure. The bucket is hanging from the

the lower hook and the upper hook is

attached to a fixed cross bar of the well. If

the mass of the bucket and the water together

is m, and the man pulls the rope with

a force F, how large is the span's acceleration

up? The mass of ropes and pulleys

can be neglected, as well as frictional forces.

http://bayimg.com/daOdPAAde [Broken]

Answer: (3F/m)-g

2. Relevant equations

F=mg and maybe F=ma

3. The attempt at a solution

Due to gravity there is a force downward. Since the mass of the bucket and the water together is m, the downward force is mg. From figure I see that the device is constructed so that the cable runs three times between the bucket and the hook before I pull it. Therefore the force required for the bucket to move upwards is F=mg/3≥.

From here I am stuck. I know that F=ma and therefore a=F/m. However, if I insert F=mg/3 and m=mg, I get the wrong answer.

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# Homework Help: Determine acceleration when lifting a bucket.

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