A tag for questions about rotational motion, including angular velocity and angular acceleration.

learn more… | top users | synonyms

0
votes
3answers
52 views

Why is moment of inertia for a point same as a ring

The moment of inertia of a point and ring are both $m R^2$. It is interesting that the formula for moment of inertia is exactly the same for both. Is there any physical reason why this is the case? I ...
0
votes
2answers
39 views

Gear ratio in bicycles using rotational motion

When we change the gears of the bicycle we are riding, we change the the disc we are currently at (which are located at the place where we pedal) to some other disc. This means the radius of the ...
19
votes
6answers
3k views

Conical train wheels

I've been reading about how the conical shape of train wheels helps trains round turns without a differential. For those who are unfamiliar with the idea, the conical shape allows the wheels to shift ...
-5
votes
1answer
34 views

Question based on friction force [closed]

How will you solve this question using high school physics? It is based on friction force (as you can see, obviously). I have problem determining the direction of friction.
0
votes
1answer
21 views

How to Calculate Engine Torque from Wheel Torque?

Not sure if this is the right place to post - so feel free to tell me to go away :) Im trying to understand how I can use wheel torque curves to estimate the engine torque vs engine rpm relationship. ...
0
votes
1answer
25 views

How to work out the gravitational potential energy of rotating rod

I know that the kinetic energy of a rotating rod is $$ KE_{rot}=\frac12I\omega^2 $$ where $I$ is the moment of inertia. But is there some way to calculate gravitational potential energy using just ...
1
vote
1answer
30 views

Observations of erratic rotation of asteroids

An asteroid generally has an irregular shape, therefore, one would expect its rotation is quite erratic in some sense. Are there any observational examples?
1
vote
1answer
53 views

About the rotating speed of a light beam which has been reflected off a rotating mirror [closed]

A light beam generated from a source reaches a rotating mirror (x m away from the source), and is reflected off to a fixed mirror ( x m from the rotating mirror ), and again back to the rotating ...
0
votes
1answer
14 views

Using Moment of Intertia Definition to Calculate Rod's Moment of Intertia [closed]

I would like to use the moment of intertia definition to calculate the moment of inertia in this problem (from 3,000 solved problems in Physics, Schaum's Outlines): "A rod of length L is composed of ...
1
vote
2answers
53 views

Minimum velocity of the particle at the highest point [closed]

A particle of mass m is fixed to one end of a light rod of length l and rotated in a vertical circular path about its other end. What is the minimum speed of the particle at the highest point? ...
1
vote
3answers
40 views

Rotation of center in rotational motion

For a wheel in pure rotational motion; Does the center rotate? Is there a point in wheel which do not rotate? What can we say about angular velocity of the center? From where we can start to use the ...
0
votes
3answers
94 views

A simple derivation of the Centripetal Acceleration Formula?

Could someone show me a simple and intuitive derivation of the Centripetal Acceleration Formula $a=v^2/r$, preferably one that does not involve calculus or advanced trigonometry?
3
votes
1answer
341 views

Why do we ignore rotational energy in monatomic gases? [duplicate]

I understand that the average energy of each degree of freedom in a thermodynamic system is $\frac12kT$. And so, for an ideal monatomic gas, there are three degrees of freedom associated with the ...
1
vote
2answers
59 views

Does gravity play a role in the Earth's equatorial bulge? [duplicate]

I'm trying to understand why the Earth bulges at the equator. But before looking at the Earth, which introduces gravity, I wanted to make sure I understood the shape of some rotating objects and ...
2
votes
1answer
103 views

Kinematics of Euler angles relative to a rotating frame

I have a rotating body $B$ and a rotating frame $F$ whose orientations are described by the quaternions $q_B$ and $q_F$ respectively. I also have the angular velocity vectors $\omega_B$ and ...
1
vote
1answer
20 views

Euler Angles with respect to base body when Euler Angles with respect to another body is known

Let's say I have a fixed base body $B_0$ with a reference frame $X_0Y_0Z_0$, and two other bodies, $B_1$ and $B_2$, rotated arbitrarily with respect to this base body. Coordinate systems fixed to ...
1
vote
1answer
99 views

On the no-faster-than-light in special relativity

In the special relativity it is well established that, in the vacuum no one can ever travel faster than light, due to the relativistic velocity addition formula. Recently I saw some silly statement ...
0
votes
1answer
39 views

Combining moments of Inertia in gear chain

I've got two objects connected by a rod along it's axis of rotation (e.g. a sphere on top of a flat cylinder rotating around it's symmetric axis). Assuming the effects of the rod are negligible, is ...
0
votes
3answers
71 views

Angular acceleration - radial & tangential

Since ever I knew that radial (angular acceleration) is equal to $ W^2 * R = V^2 / R $ and that the tangential depends in the situation (School physics & calculus). Recently I encountered the ...
1
vote
1answer
31 views

Equation of Motion for Rigid Body Motion

In a paper, eq 24 I am reading, the author mentions the equation of rigid body motion which is written as the sum of translational motion of the centre of mass, $x_G(t)$ and a rotational term about an ...
0
votes
1answer
39 views

On application of angular momentum conservation laws

Consider a situation like this: a massless ring is kept fixed at rest on a horizontal plane. A massless thin string attached at its one end to a point on the circumference of the ring while its other ...
0
votes
0answers
30 views

Force acting on a wheel of a two-wheeled self balancing bot

Proceeding further with my work on a self-balancing bot as posted here: http://bit.ly/1FfI6LK I've gotten stuck at the following equation: n = Gear ratio $K_t$ = DC motor torque constant $i_l$ = DC ...
0
votes
2answers
63 views

Yaw angle calculation for a two-wheeled inverted pendulum

[Sorry, if this is a basic question. I'm a software engineer, learning mechanical engineering concepts by trying to build a self-balancing robot] I'm unable to understand the yaw angle equation: ...
0
votes
0answers
22 views

Can't we assign any other direction for instantaneous angular velocity except along the axis of rotation? [duplicate]

We specify the direction of instantaneous angular velocity using the right hand thumb rule. I just want to know that is it just a matter of convention or we don't have any other direction for it to be ...
1
vote
0answers
41 views

how to rotate scaled-vector (orientation) by scaled-vector (rotation)

Recently I seem to have gotten the physics-engine portion of my 3D simulation/game engine [apparently] working correctly. The most convenient way to store and compute position and orientation are in ...
1
vote
0answers
43 views

How Burmester's theory converts rotary motion of the crank to linear movement?

I have been studying the mechanism of Klann's Mechanical spider and there it was written that by Burmester's theory it converts rotary motion of the crank to linear movement. I tried searching but how ...
1
vote
1answer
56 views

Simple Harmonic Motion of sphere [closed]

Problem: A solid sphere of radius 15cm is pivoted at a point on its surface. It is held so that the diameter passing through both the pivot and the center of the sphere makes a 0.15 radian ...
1
vote
1answer
31 views

Angular and linear displacement of a turning car

My illustration is supposed to show a simplified car (with just two wheels, where the front wheel has been rotated $-90 \text{ degrees}$). Let the car travel at constant speed. This means that the ...
1
vote
1answer
50 views

Normal force on a banked road & why it's larger than the gravitational force here

Please read this: http://www.askiitians.com/iit-jee-physics/mechanics/banking-of-roads.aspx From my understanding of normal forces, they are a reaction to gravitational or other forces. When a force ...
0
votes
0answers
31 views

Acceleration of an oscillating object in a frame of reference that is itself rotating!

I have been reading a paper and due to my limited knowledge of Physics, I can't move ahead. Sorry I do not know latex so, I will snip the paper and paste it here. So here goes it..... I think ...
1
vote
1answer
42 views

How do you define the total rotational energy of an object?

This problem arose when I was applying a conservation of energy argument to a mechanics problem, (a spinning coin on a table) and wasn't sure how to define the total rotational energy of the coin. At ...
0
votes
1answer
36 views

what is intertia tensor for tapered cylinder (solid and with separate inside and outside radii)

I need the inertia tensor for tapered cylinders, both solid and hollow, and if possible with independent inner and outer radii on the x and y axes (so the cross-sections of the cylinders can be an ...
0
votes
0answers
66 views

Total Energy of Inverted Pendulum

I have to find the total energy $V$ of an inverted pendulum (rod). The following parameters and their values are given: Mass $m$ and length $l$ of the pendulum $\theta$ as the angle of the ...
0
votes
2answers
59 views

How to treat an exercise about the rotational acceleration during a throw?

Because I am studying on my own, I don't have anyone to talk to about this when I don't understand, and I was wondering if someone could help me with a concept in rotational kinematics: At the ...
2
votes
3answers
212 views

Confusion regarding rotational motion!

Let us assume I have a rod of some mass m, moment of inertia I, length l and center C. If I apply a force F on C for a duration of time t, it will accelerate forward. If I apply it elsewhere, the ...
1
vote
2answers
174 views

At what point does force stop translating an object and start purely rotating it? [duplicate]

At what point (or distance) from the axis of rotation, does force applied on a rigid body stop translating and purely rotating the body? Can such a point even exist? Does the body always have to ...
3
votes
1answer
70 views

Calculating Angular Acceleration of a Rolling Object

A bowling ball of mass M = 6.50 kg, radius R = 10.0 cm, and moment of inertia I = $(2/5)MR^2$ is given an initial center of mass velocity $v_0 = 3.00 m/s$ that is parallel to a horizontal surface. ...
0
votes
1answer
51 views

Angular velocity formula for a particle?

I know that when the motion of a particle is circular about the origin then: $$\vec v=\vec \omega \times \vec r$$ But that this does not hold for any motion with a radial as well as tangential ...
1
vote
1answer
58 views

Variable Gear System [closed]

I have a variable speed gear system with 4 primary parts. I need to find the relationship between input rotational speed (wi) to output rotational speed (wo). Fig. 1 shows three of the primary ...
2
votes
0answers
85 views

Why did Feynman tell “we cannot locate earth's angular position, but we can tell that it is changing”?

I was reading "Symmetry in physics" by Feynman, where he wrote: If we perform sufficiently delicate experiments, we can tell that the earth is rotating, but not that it had rotated. In other ...
0
votes
1answer
126 views

Kinematics of a differential drive robot

(I am reposting here a question I asked on stack overflow, since it actually sits right in between programming (modeling of 2D physics) and physics proper (kinematics). I think I have the physics part ...
0
votes
1answer
37 views

Starting point for a derivation of fictitious forces

I came across this expression at the start of a derivation of fictitious forces: $$(dA/dt)_L = (dA/dt)_R + \omega \times A$$ Where the $L$ subscript refers to the laboratory (inertial) reference ...
0
votes
1answer
56 views

Is this movement possible?

My friend and I were arguing over some random facebook shared video. On this video, one guy throws up a rotating stick then, while it rotates on air, he kicks through it. Is it even possible? Or is it ...
0
votes
1answer
83 views

Representation Of Linear Velocity as Cross Product

Why is linear velocity represented as cross product of angular velocity of the particle and its position vector? Why not vice versa? (Consider rigid body rotation)
-5
votes
0answers
45 views

imbalance calculation something with f m r in calculation [closed]

A road wheel has a mass of 10kg. It is found that its centre of mass (or gravity) is offset from its centre of rotation by 2mm. Calculate the out-of-balance force acting on the wheel when the vehicle ...
1
vote
3answers
151 views

Does circular motion cause centripetal force OR does centripetal force cause circular motion?

Does circular motion cause centripetal force, or does centripetal force cause circular motion, or are they both occurring hand in hand together instantaneously? One more question: If I project a body ...
0
votes
1answer
84 views

How much energy would it take to stop Earth's rotation on its axis?

I see a lot of questions regarding situations what would happen if the world would stop spinning. This got me to wondering how much energy it would actually take to stop the world from spinning.
0
votes
2answers
38 views

Conceptual Understanding of Reference Frames correct?

The problem is as follows: A cart has a velocity to the right. There is a wheel on the cart (fastened to it). Determine the angular speed of the wheel so that the velocity at a point on the top of ...
3
votes
4answers
918 views

Puzzling : Relative motion of two points on a rotating disc

Consider two points on a radial line for a rotating disc. One point, $A$, is at the circumference and the other, $B$, is at distance $R/2$ from disc's centre. Relative velocity of $B$ w.r.t. $A$ ...
0
votes
1answer
135 views

Basic question about angular momentum

I've learned that the angular momentum of an object rotating about a fixed axis is $I \omega $. Also, in absence of external torques, $I_1 \omega_1 = I_2 \omega_2 $ (meaning, two different events). I ...