# Torque with pulleys and bucket of water

• mikefitz
In summary, a frictionless pulley with an unknown mass and a radius of 0.41 m is being used to draw water from a well. The bucket attached to the pulley has a mass of 1.53 kg and starts from rest at the top of the well. After falling for 2.04 seconds, it reaches the water 2.87 m below. The question is asking for the torque of the pulley, which can be found by calculating the tension in the rope using Newton's 2nd law and the forces acting on the bucket. The weight of the bucket does not directly exert torque on the pulley, but rather the tension in the rope does.
mikefitz
Imagine a frictionless pulley (a solid cylinder) of unknown mass M and radius r = 0.41 m is used to draw water from a well. A bucket of mass m = 1.53 kg is attached to a cord wrapped around the cylinder. A bucket starts from rest at the top of the well and falls for t = 2.04 s before hitting the water h = 2.87 m below the top of the well. Neglect the mass of the cord.

t = F*R
t=(1.53*9.81) * .41

t = 6.15 Nm??

What's the question? (Find the unknown mass of the pulley?)

Hint: What directly exerts the torque on the cylinder is the tension in the rope, not the weight of the bucket.

sorry, the question is asking what the torque is; i can't seem to figure it out for some reason?

Find the tension in the rope.

Hints: Analyze the forces acting on the bucket. Apply Newton's 2nd law. (What's the acceleration of the bucket?)

## 1. How does a pulley system affect torque?

A pulley system can increase or decrease the amount of torque required to lift a bucket of water, depending on the number and arrangement of pulleys. As more pulleys are added, the amount of force needed to lift the bucket decreases, but the distance the rope must be pulled increases.

## 2. What is the relationship between the weight of the bucket and the torque required to lift it?

The weight of the bucket directly affects the amount of torque needed to lift it. The heavier the bucket, the more torque is required to lift it. This is because torque is a product of force and distance, so the greater the weight of the bucket, the more force is needed to lift it.

## 3. How does the radius of the pulley affect the torque?

The radius of the pulley affects the amount of torque required to lift the bucket of water. A larger pulley radius will require less force to lift the bucket, while a smaller pulley radius will require more force. This is due to the relationship between torque and the distance from the axis of rotation.

## 4. How does the number of pulleys affect the mechanical advantage of the system?

The more pulleys in a system, the greater the mechanical advantage. This means that less force is required to lift the bucket of water. Each additional pulley reduces the amount of force needed by half, but increases the length of rope that must be pulled.

## 5. Can a pulley system increase the amount of work done?

No, a pulley system cannot increase the amount of work done. While it may decrease the amount of force needed to lift the bucket of water, it will increase the distance the rope must be pulled. The work done is still the same, as it is a product of force and distance.

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