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

learn more… | top users | synonyms

0
votes
0answers
30 views

Does vehicle tire mass effect efficiency?

This question has an interesting origin: A tire salesman was recommending tires (aka tyres) for a highly fuel-efficient vehicle. He said the vehicle was light (compared to most production cars), and ...
5
votes
3answers
201 views

Could moving land mass alter Earths gravity?

This is potentially a very stupid question but I'm going to ask it anyway. With all these huge buildings such as the Abu Dhabi Mosque, where an unbelievable amount of materials such as marble was ...
0
votes
2answers
85 views

Question on Angular Acceleration and Velocity

suppose, we have a body with an angular velocity, $$\vec \omega=(at,b,0)$$ where $a,b$ are constants. so the angular acceleration is clearly, $$\dot{\vec{\omega}}=(a,0,0) $$ but my question is if ...
0
votes
0answers
30 views

Relation between linear and rotational motion of molecules?

The temperature of a substance, such as an ideal gas, can be related to the root mean square speed of the molecules. For example, for gases the molecules travel at about 480 meters per second. If we ...
0
votes
1answer
23 views

Question on relative angular acceleration

I want someone to kindly check whether I am doing (understanding) the math correctly or not. So, let's consider two bodies with constant angular velocities $\omega_1 \hat y$ and y $\omega_2 \hat x$ ...
0
votes
1answer
42 views

Does the centrifugal force affect stationary objects as seen from the inertial reference frame?

If an object is moving at the same speed as a rotating/accelerating frame of reference it's in contact with but in the opposite direction (making its displacement zero), would such an object be ...
0
votes
1answer
43 views

How does angular velocity transform on the surface of a sphere?

If we consider the earth as a sphere than it will have an angular velocity of $\boldsymbol{\omega}=\omega\mathbf{e}_z=\frac{2\pi}{T}\mathbf{e}_z$ where $T\approx24h$. Now we have given a location in ...
1
vote
2answers
39 views

Angular acceleration of a spool of thread [closed]

I think this is an easy question in rotational kinematics, but--I don't seem to be understanding it on a fundamental level: Here's my work: $$ \tau \ =\ F\ r_1 $$ $$ \tau \ =\ I\ \alpha $$ $$ I\ ...
0
votes
0answers
80 views

Will future spaceships for very long distance rotate?

I have seen in the movie Interstellar and The Martian they use the model of spaceship which rotate around it's axis. This is the spaceship model from Interstellar. This is spaceship model from The ...
0
votes
1answer
34 views

Tangencial Velocity along a circle with angular acceleration

Suppose a particle walks a circle's perimeter from 0 to pi/2. Its vertical velocity is V1, constant. Its tangential speed increases as a function of theta and V1. Given V1, r, what is the ...
0
votes
1answer
50 views

Rotational motion: A cylinder, sphere and hoop rolling down a ramp [closed]

I have a question about comparing different objects in rotational motion. In this scenario: A cylinder (with moment of inertia = $\frac{1}{2}MR^2$), a sphere ($\frac{2}{5} MR^2$) and a hoop ($MR^2$) ...
0
votes
3answers
35 views

Why is the angle linearly related to time in uniform circular motion?

We say that a particle undergoes uniform circular motion if it travels a circular path at constant speed. If we assume that the center of curvature is at the origin, then in polar coordinates ...
0
votes
3answers
369 views

Acceleration of body rolling down inclined plane

Acceleration of a body rolling down an inclined plane is given by: $$\frac{g\sin\theta}{1+\frac{k^2}{r^2}}$$ $g$=acceleration due to gravity $\theta$=angle of inclined plane $k$=radius of gyration ...
1
vote
2answers
57 views

Trouble with rotational kinematics

I'm having a bit of trouble with the following homework problem: My thinking is there are only three forces acting on the laundry: the force due to centripetal acceleration, the force due to ...
0
votes
0answers
24 views

Angular velocity in body frame to displacement in lab frame?

For the case of a freely spinning symmetric top (no gravity), I derived the following equations, where $\omega_i$ is the angular velocity about a body-fixed axis: $$ \omega_1 = w_1 \cos (w_3 t) $$ $$ ...
0
votes
3answers
78 views

Magnitude of Normal Force in Circular Motion

In the above diagram an object is in vertical circular motion. At $T_0$ the object is at pos1, and at that position, I have shown the forces resolved. So $F_n-mg\cos(a)$ is the centripetal force ...
1
vote
1answer
24 views

Solid Body Rotation: ω in radians/second or rotations/second?

I am just wondering if I use the solid body rotation equation rotational energy = 1/2mr^2ω^2 and I solve for ω, and then plug in numbers, does the ω come out in radians/second, in rotations/second, ...
0
votes
1answer
39 views

Angles of rotation

I am haunted by a problem of angles of rotation. Here's my nightmare. At the origin of an inertial frame $R_0(XYZ)$, there is a rigid ball. Another reference frame $R(xyz)$ is fixed to the center of ...
1
vote
1answer
49 views

Why doesn't this differential derivation of the centripetal acceleration formula work?

I wanted to derive centripetal acceleration from scratch and tried using differential equations. But no matter what I did I hit a snag as follows: $\alpha=$ centripetal acceleration $\omega=$ ...
1
vote
5answers
78 views

Doesn't rotational KE of a rolling marble change if there is no friction to provide torque?

The question arise from the following situation: A marble at the border of a uniform bowl begins rolling within it from rest. There is enough friction in the first half the bowl for the marble to not ...
1
vote
0answers
63 views

Man on a rotating platform [closed]

A platform rotates in counterclockwise with angular velocity w. A man walks from the center of the platform to the border with constant radial velocity v' wrt the platform. $\mu_s$ is the ...
1
vote
1answer
35 views

How fast does a long object bent at the center need to be travelling in order to boomerang?

At an angle, of course. Standard pressure, average temperature, and calm wind. Bonus question: Can an object that is not bent boomerang at all? If yes, how different would the equations for this ...
0
votes
1answer
47 views

Angular velocity when a rod inclined to a wall slips and its subsequent motion observed from the axis of rotation

When a rod inclined to a wall slips, rate of change of which angle does the angular velocity represent? Is it the rate of change of angle with which the rod is inclined to the horizontal ? I'm not ...
1
vote
0answers
62 views

Trying to understand the physical intuition on finding/deriving effective rotation radii of a rigid body

This question is inspired from the answer of this If the rolling is assumed to be without slipping, we can solve the problem by conservation of energy: $$ mg \Delta h = \frac{1}{2}mv^2 + ...
1
vote
1answer
64 views

To prove uniqueness of Rotation Tensor [closed]

How can you prove that a rotation tensor which rotates some given vector is a unique tensor? Let's say we have a vector 'a' and we take a tensor product of that vector with some tensor 'Z' such that: ...
0
votes
2answers
55 views

Why does an ice hockey stick, when thrown on ice always rotate and translate together before coming to rest? Why not only rotate or only translate?

When a hockey stick is thrown on ice it simultaneously rotates and translates before stopping. Friction probably plays the main role here, along with the shape of the stick. I think maybe it is due to ...
0
votes
2answers
48 views

Cause of centripetal acceleration in a ring

Suppose a ring is rotating in space with an angular velocity $\omega .$ Then each element of the ring is having an acceleration of $m\omega^2 r$ ($r$ is the radius of the ring) but what force is ...
1
vote
0answers
57 views

Parallel axis theorem non-uniform density [closed]

The parallel axis theorem says that if the moment of inertia of a body rotating about the body's centre of mass is $I_{cm}$, then the moment of inertia of the body rotating about an axis parallel to ...
0
votes
1answer
44 views

Angular Velocity of Semicircle [closed]

In a 2-Dimensional world, a semicircle with center O, mass M and radius r is placed on the ground, with C as the point of contact. A small beetle of mass $m$ is placed at C which starts walking ...
20
votes
6answers
5k views

Can the average length of the day and night of a planet be different?

At one point in "Marvel's Agents of S.H.I.E.L.D.", some agents are on a planet where the day, defined as the length of time where the sun shines on the planet, occurs only once every 18 years for a ...
0
votes
2answers
42 views

What are our limitations on spinning a baseball sized 5 kg sphere to really fast speeds?

I know the limitation of the ball being able to hold itself together, lets assume that would not be an issue. If we were to apply a constant force over long enough time would anything short of the ...
-1
votes
3answers
72 views

Rotational kinematics [duplicate]

A particle is moving on a circular path with constant speed. Which of the following is true? (a)it posses radial acceleration. (b)it posses radial velocity. (c)it posses tangential acceleration. ...
10
votes
5answers
6k views

Earth moves how much under my feet when I jump?

If I'm standing at the equator, jump, and land 1 second later, the Earth does NOT move 1000mph (or .28 miles per second) relative to me, since my velocity while jumping is also 1000mph. However, ...
0
votes
1answer
48 views

A sphere rolling down a plank - an error in calculating its energy

Consider the following situation: A sphere with radius $r$ rolls down a plank which forms an angle $\theta$ with the horizontal axis. The starting hight of the centre of mass is $h$. We assume that ...
1
vote
2answers
82 views

Is rotational motion of the centre of mass impossible?

We know that for a system, the center of mass $CM$ moves as a particle as though all the forces on the system were acting on it. So does that mean rotational motion of the center of gravity ...
1
vote
2answers
61 views

Motion of an object in rotating frame

Yesterday I was looking at an old sloan video that describes motion in inertial and non-inertial frame. An experiment was actually like this. Two persons are sitting on the opposite side of a table ...
1
vote
0answers
24 views

Rotation, translation or both. [closed]

the square is the same material throughout, equal mass distribution. In this case, will the object rotate, translate or both and why ? Thank you.
2
votes
2answers
81 views

Calculating moment of inertia for a cylinder?

I'm trying to calculate the moment of inertia for a cylinder about a longitudinal axis, but I don't know where I went wrong with my approach. $$I=\int r^2 dm$$ Assuming constant density: ...
0
votes
0answers
50 views

Correct formulas for two wheeled robot motion

I'm trying to write a simulation of a two wheeled robot, which can be controlled by varying the speeds of his wheels, independently. However, the physics engine that I'm using can only rotate a body ...
3
votes
2answers
172 views

If the earth is spinning and we are spinning with the earth, why doesn't it take longer to go opposite the rotation?

Imagine you are on a walking type platform at an airport where you are walking with the platform where it moves you faster walking with......than against. This would be the same concept as if we were ...
1
vote
0answers
30 views

Getting an object to travel at or near light speed by adding velocities [duplicate]

Firstly I'll just give a brief example of where my query came from. I was watching the episode of Futurama where Bender meets God after being fired from the planet express ships torpedo tube. The crew ...
0
votes
1answer
29 views

Why direction of angular velocity is taken along the rotational axis?

I read that it is a convention. But what does that mean in physics? If it would have been a sign assigning matter, I could confess but what convention means here? When we decide the direction of ...
3
votes
3answers
287 views

Is angular velocity parallel to axis of rotation?

I'm reading the Wikipedia page on angular velocity. It says here of the angular velocity vector in three dimensions that “[t]he magnitude is the angular speed, and the direction describes the axis of ...
1
vote
1answer
96 views

How far does the ball travel before pure rolling motion occurs? [closed]

A bowling ball is given an initial speed $V_o = 10 \text{m/s}$ on an alley such that it initially slides without rolling. The coefficient of friction between the ball and the alley is $\mu = 0.06$. ...
1
vote
1answer
33 views

Expressing 3D orientation in alternative to Euler angles for 3D rigid body dynamics

I was unsure whether it would be best to post this in Physics, Maths, or other forums, so please say if this question is suited better elsewhere. I am trying trying to create a physics engine for a ...
2
votes
1answer
105 views

How are these marbles being accelerated?

This question refers to an effect visible starting at around 5m45s in this video1. (The question will make little sense if one has not first watched the clip.) The observation At around 5m45s we ...
0
votes
1answer
43 views

In golf, is there a rotational mechanical advantage of using a thicker grip?

I was asked to migrate this question to the physics exchange. Ok, so many professionals are now using the new SuperStroke golf grips. I am basically thinking about the concept of a bigger grip, but ...
-1
votes
1answer
52 views

Force required to rotate a rod around an axis [closed]

The problem I'm trying to solve is: How much force, momentarily applied to the rod, is required to rotate it around an axis by a given degree? Assuming there is friction applied at the axis (...
0
votes
1answer
49 views

What is the effect of torque transmitted through a gear system to the angular acceleration of a flywheel?

For a school project, I am trying to design a system that will spin a flywheel at a high rpm to store energy. My initial idea was to accelerate the flywheel via a compound gear train with an ...
4
votes
0answers
128 views

Alternate Formulation of Kinetic Energy for Lagrangian

So I have a question regarding this system: It is supposed to be a simple model of an aircraft with the fuselage idealized as a concentrated mass $M_0$ and the wings modeled as rigid bars carrying ...