# Cylindrical fishing reel problem using moment of inertia

• jhart_929
In summary, a cylindrical fishing reel with a mass of 0.85 kg and a radius of 4.5 cm has a friction clutch that exerts a restraining torque of 1.6 N·m when a fish pulls on the line. With an angular acceleration of 66 rad/s2, the force of the fish on the line can be calculated by using the moment of inertia and the equation T = a*I. Additionally, the amount of line that unwinds in .5 seconds can be found by using the equation θ = .5at^2 and accounting for the force on the line and the restraining force. It is important to remember to use radians when calculating the length of line that reels off.
jhart_929

## Homework Statement

A cylindrical fishing reel has a mass of 0.85 kg and a radius of 4.5 cm. A friction clutch in the reel exerts a restraining torque of 1.6 N·m if a fish pulls on the line. The fisherman gets a bite, and the reel begins to spin with an angular acceleration of 66 rad/s2.
a) Find the force of the fish on the line.
b) Find the amount of line that unwinds in .5 seconds.

I = .5mr^2
theta = .5at^2

## The Attempt at a Solution

I found the moment of inertia to be 8.606. What I don't understand is how to relate the torque to the moment of inertia. I don't know if my calculator should be set to radians or degrees, but I tried both ways and got them both wrong.

First of all I needs to be calculated with the radius as .045. That makes your I off by a factor of 104

I = 8.6*10-4

T = a*I

So accounting for the force on the line and the restraining force ...

F*.045 = 1.6 + 66*8.6*10-4

You have the right equation for b. Just remember that since θ is in radians, you need to provide θ*r for the length of line that reels off.

Alright thanks so much! I understand how to do it now!

## 1. What is the moment of inertia in relation to a cylindrical fishing reel problem?

The moment of inertia is a measure of an object's resistance to changes in its rotational motion. In the context of a cylindrical fishing reel, it refers to the distribution of mass around the axis of rotation, which affects how easily the reel can be turned.

## 2. How does the moment of inertia affect the performance of a fishing reel?

The moment of inertia impacts the rotational speed and ease of rotation of a fishing reel. A higher moment of inertia means it takes more force to turn the reel, resulting in slower rotation and less control over the line. A lower moment of inertia allows for faster rotation and more control over the line.

## 3. Can the moment of inertia be changed on a cylindrical fishing reel?

Yes, the moment of inertia can be altered by changing the distribution of mass on the reel. This can be achieved by adding or removing weights or by changing the design of the reel, such as using a different material or adjusting the size and shape of the spool.

## 4. How does the shape of the spool affect the moment of inertia?

The shape of the spool, specifically its radius and thickness, can significantly impact the moment of inertia. A larger and thicker spool will have a higher moment of inertia, while a smaller and thinner spool will have a lower moment of inertia. This is because the distribution of mass is different in each case, affecting the ease of rotation.

## 5. Are there any other factors that can influence the moment of inertia in a cylindrical fishing reel problem?

Aside from the shape and size of the spool, other factors that can affect the moment of inertia include the weight and placement of the fishing line, the drag force from the water, and any external forces acting on the reel. Additionally, the moment of inertia may also be influenced by friction and other factors that impact the rotation of the reel.

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