A spool of thin wire pivots on a shaft

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In summary, the conversation discusses a problem involving a pulley and a spool with friction. The mass and distance are given, and the goal is to calculate the energy lost to friction during the given time. The formula for acceleration and tension are used to find the values of a and T, which are then used to calculate the value of Qf using the formula for alpha. The value of theta is also calculated using the given distance and outer radius. However, the final answer of Ef=20.83 is questioned.
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SereneKi
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Homework Statement


Pulley with Friction
A spool of thin wire pivots on a shaft, and there is friction. The wire is pulled by a hanging mass M of 1.30 kg. After falling a distance D= 1.7 m starting from rest, the mass has a speed of 0.065 m/s. Calculate the energy lost to friction during that time.
Inner radius, ri = 0.50 m
Outer radius, r0 = 0.65 m
Icm= 0.96 kg/m2.


The Attempt at a Solution



a=v^2/2*D -> a=0.0036
T=m(g-v^2/2*D) -> T=12.24
alpha=a/r0=(r0*T-Qf)/Icm -> Qf=7.951
theta=D/r0 ->2.62
Ef=theta*Qf -> Ef=20.83

what am I doing wrong?
 
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  • #2
Hi SereneKi! :smile:

I don't understand the question …

is there a pulley and a spool?

between what surfaces is the friction?

what is the relevance of the outer radius of the spool? :confused:
 

Related to A spool of thin wire pivots on a shaft

What is a spool of thin wire and how does it pivot?

A spool of thin wire is a cylindrical object that contains a length of thin wire wound around it. It pivots on a shaft, which means it rotates or turns around a central axis. This allows the wire to be wound or unwound from the spool.

What is the purpose of a spool of thin wire?

A spool of thin wire is often used for storage and transportation of wire, as it keeps the wire neatly wound and prevents tangling. It can also be used in various applications such as electrical wiring, sewing, and fishing.

What types of wire can be wound on a spool?

A spool of thin wire can hold various types of wire, including copper, aluminum, steel, and other alloys. The thickness of the wire can also vary, depending on the specific application it is intended for.

How does the pivot mechanism work on a spool of thin wire?

The pivot mechanism on a spool of thin wire usually consists of a shaft inserted through the center of the spool, allowing it to rotate. Some spools may also have additional components such as bearings or gears to facilitate smoother pivoting.

What factors should be considered when choosing a spool of thin wire?

When selecting a spool of thin wire, it is important to consider the type and thickness of the wire, the size and material of the spool, and the intended use. It is also important to ensure that the pivot mechanism is sturdy and durable to avoid any issues during use.

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