# Test Question - Pulleys and Rubberbands

• Mgeiss
In summary, the conversation discusses a question on a test about two identical rubber bands connecting masses A and B to a string over a frictionless pulley. The question asks which band will have a greater amount of stretch, and the answer is that they will stretch the same amount due to the same amount of force acting on them. The concept of equilibrium and the relationship between the tension in the rubber bands and the string are also mentioned.
Mgeiss
I missed this question on the test and I don't get it...

I attached a scanned image of the question. If you can't make out the text it reads:

Two identical rubber bands connect masses A and B to a string over a frictionless pulley of negligible mass. The amount of stretch is greater in the band that connects to:
A
B
Both the same

#### Attachments

• TestQuestion.jpg
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If the two rubber bands are identical, they must stretch the same amount for the same amount of force acting on them. If you have studied springs, that's a good way to look at the way the bands work. (F=kx, same k)
The next part to understanding this problem is considering how the free body diagram would look for each weight, specifically the tension on the bands. Note that the system is at equilibrium and consider the implications of that.

There's no reason to think that the system is in equilibrium. (Are the masses equal?)

Hint: How does the tension in the rubber bands relate to the tension in the string?

## 1. What is a pulley and how does it work?

A pulley is a simple machine that consists of a wheel with a groove around its circumference and a rope or belt that runs around the groove. When a force is applied to one end of the rope, it causes the wheel to rotate. This allows for the transfer of force from one point to another, making it easier to lift heavy objects.

## 2. What are the different types of pulleys?

There are three main types of pulleys: fixed, movable, and compound. A fixed pulley is attached to a stationary object and only changes the direction of the force. A movable pulley is attached to the object being lifted and moves with it, reducing the amount of force needed. A compound pulley is a combination of fixed and movable pulleys, allowing for both direction change and force reduction.

## 3. How do rubber bands affect the function of a pulley?

Rubber bands can be used in a pulley system to increase the friction between the rope and the wheel, preventing the rope from slipping. They can also help to keep the rope in place and prevent it from coming off the wheel. Additionally, rubber bands can be used to provide elasticity and reduce shock in the pulley system.

## 4. What are some practical applications of pulleys and rubber bands?

Pulleys and rubber bands are used in a variety of applications, such as in elevators, cranes, and construction equipment. They are also commonly used in exercise equipment, such as weightlifting machines and resistance bands. In everyday life, pulleys and rubber bands can also be found in window blinds, clotheslines, and garage doors.

## 5. Are there any limitations to using pulleys and rubber bands?

While pulleys and rubber bands have many benefits, there are also some limitations to consider. For example, the use of rubber bands can cause the pulley system to stretch over time, leading to decreased efficiency. Additionally, pulleys can only redirect force, not multiply it, so they cannot be used to lift objects that are heavier than the applied force.

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