What Is the Tension and Kinetic Friction in This Blocks and Pulleys System?

In summary, blocks and pulleys work together in a system to make it easier to lift heavy objects by distributing the weight across multiple ropes and pulleys. This reduces the amount of force needed to lift the object, allowing a person to lift something that would normally be too heavy to lift on their own. The mechanical advantage of using blocks and pulleys is the ratio between the weight of the object being lifted and the force needed to lift it. The number of pulleys needed for a block and tackle system depends on the weight of the object being lifted and the desired mechanical advantage. There are two types of pulleys: fixed and movable. A fixed pulley only changes the direction of the force, while a movable pulley also provides a mechanical
  • #1
FabricWarp
2
0
Three Blocks total, Two on sides hanging off the table, and one Block on table in the middle of the two outer blocks. . . symmetrical.

block1 from left has a mass of M, hanging and connected to a pulley, which is the connected to Block 2(on a table) with Mass of 2M, Block three is also hanging but with mass of 2M. If acceleration is .5m/s^2, What is the Tension on the first string?
what is the Kinetic friction of Black 2 on Table?

Fnet=Ma

I started by writing that Block 3= 2Mg-T2=2Ma
Block 2= T2-T1=2Ma
Block 1= T1-Mg=Ma
I then connected Block3 to Block2, since they share T2
I would add forces but tensions would simply cancel out, at times even masses and Tension, leaving me with known variables=known variables, makes not sense. I tried many ways. This is all the info the book gives, but I feel I'm missing a key idea.


This has been driving me insane.
The tension question was given to me on a test, which I failed answering correctly.
The Kinetic question, I know from back of book, the coefficient of kinetic friction is = .37
But I don't know how exactly how they got to it. Some one please help.
 
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  • #2
FabricWarp said:
I started by writing that Block 3= 2Mg-T2=2Ma
Good.
Block 2= T2-T1=2Ma
Don't forget that friction acts on Block 2.
Block 1= T1-Mg=Ma
Good.

Correct your equation for Block 2 and you'll be able to solve for the friction, then use that to find μ.
 
  • #3
Welcome to PF!

Hi FabricWarp! Welcome to PF! :smile:

(instead of using "SIZE" tags, try using the X2 and X2 tags just above the Reply box :wink:)
FabricWarp said:
Block 2= T2-T1=2Ma

ooh, you're missing the obvious … you need a 2µMg somewhere in there, don't you? :smile:
 

FAQ: What Is the Tension and Kinetic Friction in This Blocks and Pulleys System?

How do blocks and pulleys work together?

Blocks and pulleys work together to make it easier to lift heavy objects by distributing the weight across multiple ropes and pulleys. The pulleys reduce the amount of force needed to lift the object, making it possible for a person to lift something that would normally be too heavy to lift on their own.

What is the mechanical advantage of using blocks and pulleys?

The mechanical advantage of using blocks and pulleys is the ratio between the weight of the object being lifted and the force needed to lift it. For example, if a block and tackle system has a mechanical advantage of 4, it means that the force needed to lift the object is one-fourth of the weight of the object.

How do you determine the number of pulleys needed for a block and tackle system?

The number of pulleys needed for a block and tackle system depends on the weight of the object being lifted and the desired mechanical advantage. To determine the number of pulleys, divide the weight of the object by the desired mechanical advantage. For example, if the object weighs 100 pounds and you want a mechanical advantage of 4, you would need 25 pulleys (100/4=25).

What is the difference between a fixed and a movable pulley?

A fixed pulley is attached to a stationary object, while a movable pulley is attached to the object being lifted. A fixed pulley only changes the direction of the force, while a movable pulley also provides a mechanical advantage by distributing the weight across multiple ropes and pulleys.

What are some real-life applications of blocks and pulleys?

Blocks and pulleys are used in a variety of industries, from construction and transportation to theater and entertainment. They are also commonly used in simple machines, such as cranes and elevators, to lift heavy objects. In everyday life, blocks and pulleys can be found in window blinds, flagpoles, and even exercise equipment.

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