• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Relative rotational motion on a disc

Homework Statement
##A## oscillates along the central position ##O## with amplitude ##5 cm## at a frecuency ##2 hz## such that its displacement measured in ##cm## in function of time is governed by ##x=5sin(4 \pi t)##, where ##t## is measured in seconds. An angular acceleration around ##O## is applied to the disc with an amplitude ##20 rad## at a frequency ##4 hz## such that ##\theta =0.20sin(8 \pi t)##. Determine the acceleration of A for ##x=0 cm## and ##x= 5 cm##.
Homework Equations
##\vec a=\vec a_B + \vec{\dot \omega} X \vec r + \vec \omega X \vec \omega X \vec r + 2. \vec \omega . \vec v_{rel} + \vec a_{rel}##
The first doubt that comes to my mind is "I have to determine the acceleration with respect to what?", because the problem doesn't tell. Then, I have some problems when having to plug the data in the formula of acceleration. ##\vec a_B=0## because the origin isn't accelerated, ##\vec{\dot \omega} X \vec r## would be ##x=5sin(4 \pi .5)## (in the second case), and then what numbers should I plug in ##\vec \omega X \vec \omega X \vec r##, ##2. \vec \omega . \vec v_{rel}## and ##\vec a_{rel}##?
I don't understand relative rotational motion very well. I mean, I just have to plug the data in the formula, but I don't know what's the data that I have.


20190906_20202777.jpg
 

haruspex

Science Advisor
Homework Helper
Insights Author
Gold Member
2018 Award
31,505
4,629
Homework Statement: ##A## oscillates along the central position ##O## with amplitude ##5 cm## at a frecuency ##2 hz## such that its displacement measured in ##cm## in function of time is governed by ##x=5sin(4 \pi t)##, where ##t## is measured in seconds. An angular acceleration around ##O## is applied to the disc with an amplitude ##20 rad## at a frequency ##4 hz## such that ##\theta =0.20sin(8 \pi t)##. Determine the acceleration of A for ##x=0 cm## and ##x= 5 cm##.
Homework Equations: ##\vec a=\vec a_B + \vec{\dot \omega} X \vec r + \vec \omega X \vec \omega X \vec r + 2. \vec \omega . \vec v_{rel} + \vec a_{rel}##

The first doubt that comes to my mind is "I have to determine the acceleration with respect to what?", because the problem doesn't tell. Then, I have some problems when having to plug the data in the formula of acceleration. ##\vec a_B=0## because the origin isn't accelerated, ##\vec{\dot \omega} X \vec r## would be ##x=5sin(4 \pi .5)## (in the second case), and then what numbers should I plug in ##\vec \omega X \vec \omega X \vec r##, ##2. \vec \omega . \vec v_{rel}## and ##\vec a_{rel}##?
I don't understand relative rotational motion very well. I mean, I just have to plug the data in the formula, but I don't know what's the data that I have.


View attachment 249344
There's something wrong with your equation. ##2. \vec \omega . \vec v_{rel}## would be a scalar.
For the cross products, use \times; and the triple cross product needs parentheses.

No equation is meaningful without a statement of the context and definitions of the variables. Please state these for your relevant equation.
 

Want to reply to this thread?

"Relative rotational motion on a disc" You must log in or register to reply here.

Related Threads for: Relative rotational motion on a disc

Replies
12
Views
1K
  • Posted
Replies
5
Views
4K
  • Posted
Replies
5
Views
2K
Replies
1
Views
1K
Replies
5
Views
2K
Replies
3
Views
2K
  • Posted
Replies
2
Views
1K
Replies
4
Views
2K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top