String rotating to make a cone, find period and tension

In summary, to solve this problem we need to use the given information to find the velocity of the mass, which can then be used to calculate the tension in the string and the period of the motion.
  • #1
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Homework Statement


"A mass m = 16.0 kg is attached to the lower end of a massless string of length L = 71.0 cm. The upper
end of the string is held fixed. Suppose that the mass moves in a circle at constant speed, and that the
string makes an angle theta = 25deg with the vertical, as shown in the figure."
(See attachment on page 2)


Homework Equations


T = 2pi*r/v


The Attempt at a Solution


I found tension = (16)(9.8)/(cos25deg) (not sure if this is the correct answer though but I think it is)

T = 2pi*r/v I found radius = 0.71m * (sin25deg)
but I need to find velocity I'm guessing so that I can get period T.

Any help would be greatly appreciated!
Thanks in advance!
 

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  • #2




Thank you for your post. I would like to offer some guidance on how to approach this problem.

Firstly, it is important to carefully read and understand the given information. From the information provided, we can see that a mass of 16.0 kg is attached to a string of length 71.0 cm, and that the mass moves in a circle at constant speed while the string makes an angle of 25 degrees with the vertical. This forms a right triangle, where the hypotenuse is the length of the string and the adjacent side is the radius of the circle.

Next, we can use the given equation T = 2pi*r/v to find the tension in the string. However, to do so, we need to first find the velocity of the mass. To find the velocity, we can use the fact that the mass moves at a constant speed in a circle, which means that its centripetal acceleration is constant. We can use the equation a = v^2/r to find the velocity, where a is the centripetal acceleration and r is the radius of the circle.

Once we have found the velocity, we can substitute it into the equation for tension to find the value of T. From there, we can use the equation for period T = 2pi*r/v to find the period of the motion.

I hope this helps. Good luck with your problem!
 

1. What is the concept behind string rotating to make a cone?

The concept behind string rotating to make a cone is based on the principle of centrifugal force. When a string is rotated at a constant speed, the centrifugal force acts as a tension force that keeps the string taut and causes it to form a cone shape.

2. How is the period of string rotation calculated in this scenario?

The period of string rotation can be calculated using the formula T = 2π√(L/g), where T is the period, L is the length of the string, and g is the acceleration due to gravity. This formula is derived from the equation for the centripetal force, which is equal to the tension force in this scenario.

3. What factors affect the tension in the string during rotation?

The tension in the string during rotation is affected by several factors such as the speed of rotation, the length of the string, and the mass of the object attached to the string. In general, a higher speed of rotation or a longer string will result in a higher tension, while a heavier object will decrease the tension.

4. Can the cone shape formed by the string be used to measure the period of rotation?

Yes, the cone shape formed by the string can be used to measure the period of rotation. By measuring the height and radius of the cone, the length of the string can be calculated and then used in the formula for period mentioned above to determine the period of rotation.

5. How is this concept relevant in real-world applications?

The concept of string rotating to make a cone has several real-world applications, such as in the design of centrifugal separators and centrifugal pumps. It is also used in physics experiments to demonstrate the principles of centripetal and centrifugal forces.

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