# What Torque Is Required to Raise a Water Bucket from a Well?

• OierL
In summary: So, all the answers are close to your answer.In summary, the conversation discusses the problem of raising a bucket of water from a well using a rope attached to a cylinder that is turned by a crank. The question asks for the torque required to raise the bucket at a constant speed. The solution involves using the equations for force and torque and taking into account the mass of the bucket and the cylinder. The correct answer is most likely option b, 24 N.m, although the given data for the cylinder may cause some confusion.
OierL

## Homework Statement

Water is drawn from a well in a bucket tied to the end of a rope whose other end wraps around a cylinder of mass 50 kg and diameter 25 cm. As you turn this cylinder with a crank, the rope raises the bucket. If the mass of a bucket of water is 20 kg, what torque must you apply to the crank to raise the bucket of water at a constant speed?

Solution:
a. 2.5 N.m
b. 24 N.m
c. 80 N.m
d. 2400 N.m
e. 49 N.m
I don't know which one is the correct solution and why they give me the data of the weight of the cylinder.

## Homework Equations

∑F=m*a
∑M=F*r and ∑M=I*α

## The Attempt at a Solution

If we raise the bucket at a constant speed, ∑M=0
-m(bucket)*g + T=m*α*r=0 (constant speed) ⇒ T=m*g
∑M= (-T*R) + (τ)=0 (Being τ the torque I apply) ⇒ -(m*g*R) + τ=0 ⇒ τ= 20 * 9,8 * (0,25/2)
τ=24,5N*m

Your answer looks fine. The mass of the cylinder will be needed if the bucket has a given acceleration different from zero.

Your solution looks good to me. The mass of the cylinder was just to throw you off.

Ok thank you! Now I'll have to think which of the solutions choose, since my result is different from the others hahaha.

OierL said:
Now I'll have to think which of the solutions choose, since my result is different from the others hahaha.
The choice should be clear.

OierL said:
Ok thank you! Now I'll have to think which of the solutions choose, since my result is different from the others hahaha.
That should not be too hard. Note that the numbers are given to two significant figures.

## 1. What is torque and why is it important?

Torque is a measure of force that causes an object to rotate around an axis. It is important because it is necessary for many machines and devices to function properly. Without the correct amount of torque, machines may not work efficiently or may even break down.

## 2. How is torque calculated?

Torque is calculated by multiplying the force applied to an object by the distance from the axis of rotation to the point where the force is applied. Mathematically, it is represented as torque = force x distance.

## 3. What units are used to measure torque?

The standard unit for torque is Newton-meters (Nm) in the metric system and foot-pounds (ft-lb) in the imperial system. Other units such as kilogram-meters (kg-m) and inch-pounds (in-lb) may also be used.

## 4. How do I know how much torque to apply?

The amount of torque to apply depends on the specific object or machine you are working with. It is important to consult the manufacturer's instructions or reference a torque chart to determine the correct amount of torque for a given application.

## 5. What happens if I apply too much or too little torque?

Applying too much torque can cause damage to the object or machine, while applying too little torque can result in the object not functioning properly. It is important to use the correct amount of torque to ensure the object's optimal performance and longevity.

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