# The mass of an object with pulleys

• Francis Hannah
In summary, the tension in the pulley system is equal on all sides and is calculated using the cosine function. The angle of 37.9 degrees does not determine the force required to lift the block. The mass of the block can be calculated using the force and the angle, resulting in a value of 17.88 kg or lower. It is important to draw a free body diagram to understand the forces acting on the mass.
Francis Hannah

A block is lifted by the pulley. Where θ=37.9 degrees and F=112N, find the mass of the block in kg.

I know that tension T1=T2=T3.

So, T3=112⋅cos(7.1)=111.14

Hence, T1 and T2 are equal to 111.14 as well.

Thus, mg=(2)⋅(111.14)⋅cos(37.9)=175.40?

And thus the mass is < 175.40/9.81 ⇒ mass < 17.88 kg?

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What does the 7.1 degree angle have to do with anything?

Bystander
Orodruin said:
What does the 7.1 degree angle have to do with anything?

[

Wouldn't T3 have to be at the same angle as T1 and T2?

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No. Any particular reason why you think so?

Orodruin said:
No. Any particular reason why you think so?

Oh, does the angle not determine how much force is required to lift the block?

Jake Wrightson said:
Oh, does the angle not determine how much force is required to lift the block?
No. Again, why do you think it would?

Now, the angle ##\theta## will influence the force. I suggest you draw a free body diagram for the mass.

Orodruin said:
No. Again, why do you think it would?

Now, the angle ##\theta## will influence the force. I suggest you draw a free body diagram for the mass.

I see, thank you for your help.

So mg is equal to (2)(112)cos(37.9)?

Yes. For the future, please state your reasoning more clearly. It will make it easier to help you. It will also generally help if you answer direct questions.

Francis Hannah

## 1. What is the mass of an object with pulleys?

The mass of an object with pulleys is the same as the mass of the object without pulleys. Pulleys do not add or subtract from the mass of an object.

## 2. How does the number of pulleys affect the mass of an object?

The number of pulleys does not affect the mass of an object. As mentioned before, pulleys do not add or subtract from the mass of an object.

## 3. Can pulleys change the weight of an object?

No, pulleys do not change the weight of an object. The weight of an object is determined by the force of gravity acting on it, which is not affected by the use of pulleys.

## 4. Is there a limit to the mass that can be lifted with pulleys?

Theoretically, there is no limit to the mass that can be lifted with pulleys. However, the more pulleys are used, the more friction and energy loss occurs, making it difficult to lift heavier objects. Additionally, the strength of the materials used for the pulleys and ropes also plays a role in determining the maximum mass that can be lifted.

## 5. How can the mass of an object with pulleys be calculated?

The mass of an object with pulleys can be calculated by measuring the force needed to lift the object using a pulley system and using the formula F=ma, where F is the force, m is the mass, and a is the acceleration due to gravity. The mass can also be determined by using a balance scale or by subtracting the mass of the pulleys and rope from the total weight of the object and pulley system.

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