Calculating Yo-Yo Acceleration, Velocity, and Frequency

AI Thread Summary
The discussion revolves around calculating the dynamics of a yo-yo in free fall, specifically its acceleration, forces acting on the suspension, and its velocity and frequency during motion. The initial assumption that the yo-yo experiences an acceleration of 9.81 m/s² is challenged, as the actual acceleration must account for both translational and rotational dynamics, which results in a lower value. Participants express confusion about the forces acting on the suspension during both downward and upward motions, with clarification needed on how these forces change during the yo-yo's reversal. The complexity of the yo-yo's design, including the use of two strings and a central rod, is noted as a factor that complicates the calculations. Overall, the discussion highlights the need for a deeper understanding of the physics involved in the motion of the yo-yo.
Icheb
Messages
42
Reaction score
0
I have a yo-yo of mass 0.5kg, which consists of a solid, homogeneous disc of radius 5cm. It is connected via a rod that is assumed to be weightless of radius 0.5cm to two strings of length 0.5m.
Now the yo-yo is in the motion of falling down.

a) What acceleration does the yo-yo receive?

Wouldn't that just be 9.81m/s^2 since no other forces are acting on the yo-yo?

b) Which force is acting on the suspension?

I'm assuming the yo-yo is still in the downward motion, so why would there be a force acting on the suspension? It's basically falling freely.

c) What's the highest downward velocity and what is the highest frequency of revolution the yo-yo reaches?

To calculate the velocity at the turning point I would use s=1/2 * at^2 and solve it for t so I know how long it took to reach the point. This t I would then insert in v=a*t to get the velocity at that point. Right?

To calculate the frequency I can use the radius of the rod, which is 0.5cm, to calculate its circumference. With the circumference I can calculate what distance the yo-yo travels in one revolution and then I just have to calculate how often it has to turn in one second to reach the velocity at the lowest point. Right?

d) At the end the yo-yo changes its direction. Which average force acts during the reversal of the process, which occurs within half a revolution of the yo-yo, additionally on the suspension?

This is where I'm confused. When the yo-yo hits the end of the strings, it has a force of f=m*a=0.5kg*9.81m/^2 and then this force acts on the suspension because the suspension has to stop the movement. During the reversal process that force gets smaller and smaller until the yo-yo is flying up again.
Is there another formula for the force which I should be using or is my approach flawed? I'm asking because it mentions how long the process takes and I'm not using that information.

e) Which force is acting on the suspension during the upward motion?

Shouldn't this be similar to b), where there is no force acting on the suspension itself because it's just flying upwards?
 
Physics news on Phys.org
I cannot make sense out of the description of the yo-yo. A yo-yo is not a solid disk. The typical yo-yo is made of two disks connected by a small rod with one string wrapped around the rod. If that is what you have, the questions you are being asked make sense, but I don't see what two strings has to do with the problem, and I can't visulaize the rod described in this problem.

If we can assume this thing really is a yo-yo and that the rod is the usual central rod with one string wrapped around it that is fixed at the other end, then the acceleration will be far less than g. You need to consider the translational and rotational accelerations at the same time.
 
It would be something like this:
http://img170.imageshack.us/img170/2010/maxwellradsmallwx2.jpg

For some reason they called it a yo-yo.
 
Last edited by a moderator:
Icheb said:
It would be something like this:

For some reason they called it a yo-yo.

Ah... and now I see the reason for two strings. A bit unconventional, but it will still act like any other yo-yo. Do you understand why the acceleration is less than g? Can you figure out what it should be?
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top