# Trying to Understand Rotational Motion

• Studying
• Arman777
In summary: Can somebody explain in simple terms what angular momentum is,and its importance?Angular momentum is a vector quantity that describes the rotational motion of a body. It is defined as the product of the mass of the object and the angular velocity of the object.
Arman777
Gold Member
I am really troubling to understand the rotational motion concept.Like angular accceleration,angular velocity torque ext.I don't know, I listened my professor's video lectures, I looked some online course pdfs but I need to learn the basics and I need more basic practice for simple understanding .

Thanks

Arman777 said:
I am really troubling to understand the rotational motion concept.Like angular accceleration,angular velocity torque ext.I don't know I listened my prof video lectures,I look some online course pdfs but I need more basic practice for simple understanding and learning the basics.Any advice ?

What you are describing is rather vague. If we give you "advice", how are we to know if this is something that you had encountered already and, obviously, is not working.

What you should do is pick out ONE example of a problem that you cannot solve, go to the Homework forum and show what you have done, and then indicate where you got stuck. Then wait for help or queries from other members here.

Once it is solved, see if you've understood why you got stuck, and if you've understood something that you didn't before. Go find another similar problem, and try solving it. If you can, there's a good chance that you've overcome this obstacle. If not, then repeat the above.

Otherwise, we are left with some vague idea that you have problems in rotational dynamics without really any specific information on what really is the source of the issue.

Zz.

Arman777 said:
I am really troubling to understand the rotational motion concept.Like angular accceleration,angular velocity torque ext.I don't know, I listened my professor's video lectures, I looked some online course pdfs but I need to learn the basics and I need more basic practice for simple understanding .

Thanks
https://en.wikipedia.org/wiki/Rotation_around_a_fixed_axis

Scroll down to "equations of kinematics"

berkeman
ZapperZ said:
What you are describing is rather vague. If we give you "advice", how are we to know if this is something that you had encountered already and, obviously, is not working.

What you should do is pick out ONE example of a problem that you cannot solve, go to the Homework forum and show what you have done, and then indicate where you got stuck. Then wait for help or queries from other members here.

Once it is solved, see if you've understood why you got stuck, and if you've understood something that you didn't before. Go find another similar problem, and try solving it. If you can, there's a good chance that you've overcome this obstacle. If not, then repeat the above.

Otherwise, we are left with some vague idea that you have problems in rotational dynamics without really any specific information on what really is the source of the issue.

Zz.

Well you are right.I know the all equations.Just putting them together and base them on a logic is much more harder to me for this subject (I don't know why )

Arman777 said:
Well you are right.I know the all equations.Just putting them together and base them on a logic is much more harder to me for this subject (I don't know why )
Look at the data. Given are the initial angular velocity, ωi=1.5 rad/s2, and the final one, ωf=0 as the wheel stops. The angular displacement is also given, θ=80π. You find the relation among the kinematic equations
.
Substitute the given data and solve for t.

I am trying to solve the problems on my book but going terrible..I can't do..And I can't ask here one by one-takes too much time

Arman777 said:
I am trying to solve the problems on my book but going terrible..I can't do..And I can't ask here one by one-takes too much time

Then how are you going to learn?

You don't seem to understand what I have told you. Go to the HW forum, and ask JUST ONE question first. Try to understand where you got stuck, and how to unstuck yourself.

Then, there is a good chance that, if things click, you will learn something by solving that problem. See if you can apply that understanding to another problem. In other words, while you may have a lot of problem you can't solve now, maybe that number will be reduced AFTER you understand how to do one.

Besides, rotational dynamics is no different than the linear dynamics problem. If you can solve the latter, there is no reason not to be able to solve the former. The concept is the same, and the equations are similar!

Zz.

ZapperZ said:
Besides, rotational dynamics is no different than the linear dynamics problem. If you can solve the latter, there is no reason not to be able to solve the former. The concept is the same, and the equations are similar!

Yeah right,I can solve kinematics easily but rotational kinematics comes so hard.Maybe cause of my native language,maybe I don't fully understand the questions.Ok I ll ask now

Arman777 said:
Yeah right,I can solve kinematics easily but rotational kinematics comes so hard.Maybe cause of my native language,maybe I don't fully understand the questions.Ok I ll ask now

Then you are not seeing it.

This is a scan of what I have written on the white board in my class to drill into the students that rotational motion is no different than linear motion.

If you can do linear motion problems, but you can't do rotational motion problems, then you need to figure out why you are having problems here.

Zz.

ZapperZ said:
Then you are not seeing it.

This is a scan of what I have written on the white board in my class to drill into the students that rotational motion is no different than linear motion.

If you can do linear motion problems, but you can't do rotational motion problems, then you need to figure out why you are having problems here.

Zz.

I know they look all the same..I really don't know where I am doing wrong.Thanks :)

I guess I understand.In kinematics its simple,m/s m/s^2 that's all. Here,rad/sec rad/min rev/s rev/min and sometimes there's angels sometimes f sometimes we convert that w and makes me confused everytime

I looked my book once more and I can do most of the questions now,just amazing

## 1. What is rotational motion?

Rotational motion is the movement of an object around an axis or fixed point, resulting in a circular or curved path.

## 2. What causes rotational motion?

Rotational motion is caused by the application of a torque or rotational force to an object. This can be achieved through the use of a force acting at a distance from the axis of rotation or through the application of a force at the axis of rotation itself.

## 3. How is rotational motion measured?

Rotational motion is typically measured using units of angular displacement, velocity, and acceleration. Angular displacement is measured in radians or degrees, angular velocity is measured in radians per second, and angular acceleration is measured in radians per second squared.

## 4. What is the difference between rotational and linear motion?

Rotational motion involves movement around a fixed point, while linear motion involves movement in a straight line. Additionally, rotational motion is typically measured using units of angular displacement, velocity, and acceleration, while linear motion is measured using units of distance, velocity, and acceleration.

## 5. How is rotational motion related to Newton's laws of motion?

Rotational motion can be explained using Newton's laws of motion, specifically the second and third laws. The second law states that the net torque applied to an object is equal to the product of the object's moment of inertia and its angular acceleration. The third law states that for every action, there is an equal and opposite reaction, which can be seen in the way rotational forces are applied to an object.

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