A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
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1answer
217 views
Is this simulation following real physics?
I am trying to simulate a game in Box2D(Physics engine). The game that I am trying to simulate is very simple and can be found here: http://www.makaimedia.com/#/speartoss
What I want to know is that, ...
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1answer
56 views
Physics of the point of contact for a spinning top
I understand how spinning tops don't tip over, cf. e.g. this and this Phys.SE questions. What I'm more interested is in identifying the factors that determine the direction the spinning top moves to?
...
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1answer
182 views
Non-commutative property of rotation
Addition of angles are non-commutative in three dimensions. Hence some other angular vector quantities like angular velocity, momentum become non-commutative. What is the physical significance of this ...
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1answer
42 views
Rotation of diatomic homonuclear molecule
I know that the rotation energy of a diatomic homonuclear molecule is $E_{Rot}=\frac{\hbar J(J+1)}{R^2 M}$. Does the axis of rotation depend on $J$? With respect to which axis does the molecule for ...
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1answer
164 views
What controls whether a ball will skid or roll?
A billard ball is struck with a cue. The line of action of the applied impulse is horizontal and passes through the center of the ball. The initial velocity $v_0$ of the ball, its radius $R$, its mass ...
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1answer
163 views
Determining axis of rotation from angular speeds about axes
I think my pure-math head is messing with me on the question below: my physics and CS friends both seemed to think it was a simple computational thing, and my program says the method works, but now ...
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1answer
263 views
What techniques can be used to analyze a rod rotating about the edge of a table?
A uniform rod of length $4x$ is rotating
about the edge $O$ of the table. (The rod does not fall off the table.) The centre of mass $G$ of the rod is distance $x$ away from $O$. The rod is making ...
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2answers
438 views
Altering Venus rotational speed to match Earth's via weather manipulation
Venus rotates approximately 6.5 km an hour Earth rotates approximately 1650 km/h how fast could we speed up Venus's rotation via only weather manipulation ( maybe a giant fractal lens between Venus ...
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2answers
179 views
Problem based on Rotational Motion #2
One fourth length of a Uniform Rod of mass $m$ and length $x$ is placed on rough horizontal surface and it is held stationary by means of a light thread as shown in the figure. The thread is brunt ...
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1answer
225 views
Problem based on Rotational Motion [closed]
A spool of mass $\mathsf m$ and inner radius $\mathsf r$ and outer radius $\mathsf{2r}$, having moment of inertia $\Large\mathsf{\frac{mr^2}{2}}$ is made to roll without sliding on a rough ...
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1answer
1k views
Would a light or a heavy ball roll fastest down a slope?
A small, light ball and a larger, heavier ball are released from the top of a slope.
Which will move further? which will come down faster?
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2answers
214 views
Why do balls in a spinning ellipsoid move to the minor axis plane?
There is a question concerning the Physics of a small child's tall that has been bothering me for some time now. I have investigated this to a small degree, but I have not been able to find a ...
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1answer
210 views
Artificial Gravity - Spinning Station Questions II
In an answer to Artificial Gravity - Spinning Station Questions Vintage wrote:
A theoretical space station of radius 900 meters, doing a complete rotation every 60 seconds (in order to generate ...
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1answer
200 views
Top spun up with string under tension problem [duplicate]
Possible Duplicate:
Homework about spinning top
I have a top with an unknown mass. It has a moment of inertia of 4.00 * 10^-7 kgm^2
a string is wrapped around the top and pulls it so that ...
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1answer
599 views
Relation of angular speed of a rigid body to Euler's Angles
My Question was like this and i have realised few things and still have some doubts
I have a book in which a paragraph goes like this
Now, $\dot\phi$, $\dot \theta$,
$\dot\psi$ are respectively ...
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1answer
686 views
Finding angular acceleration from torque
We have to analyze this video
Givens:
An applied net torque due to the wind on the windmill is equal to 1500 N*m.
Each (of the 3) propeller props weighs approximately 45 Kg and has a Moment of ...
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2answers
45 views
Deriving $T = F\ r = I\alpha$ for a rigid body
For a single point mass :
$\tau=F_{t}r=ma_tr=(m r^2)\alpha = I\alpha$
For multiple point masses bound together : $\sum \tau_i = (m_ir_i^2)\alpha = I\alpha$
But how do we go from that to $I\alpha = ...
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1answer
79 views
Double Compound Pendulum: why use inertia about the center of mass for bottom pendulum?
I'm trying to wrap my head around the kinetic energy of a double compound pendulum, like the one shown in the Wikipedia article on double pendulums.
I know for computing the kinetic energy of the ...
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1answer
144 views
Cylinder rolling down an inclined plane held by a string
A cylinder of mass M and radius R is in static equilibrium as shown in the diagram. The cylinder
rests on an inclined plane making an angle with the horizontal and is held by a horizontal string
...
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0answers
61 views
Limitations on the choice of axis of rotation regarding rolling wheels
Consider a situation where a wheel is rolling without friction on a level surface. Call the center of the wheel $C$, the point where the wheel contacts the ground $G$, and some arbitrary other point ...
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0answers
249 views
Neglecting friction on a pulley?
So, this is how the problem looks:
http://www.aplusphysics.com/courses/honors/dynamics/images/Atwood%20Problem.png
Plus, the pulley is suspended on a cord at its center and hanging from the ceiling.
...
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0answers
47 views
Fading transition and rotation of and object in 2D
I'm looking for sources about I guess dynamics subject.
The model I'd like to solve is reduced to a question of:
How does a force applied on a certain point of an object results in both fading ...
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0answers
242 views
Rotational Dynamics Problem-Rod slipping against block
A uniform rod of mass m and length l is pivoted at point O. The rod is initially in vertical position and touching a block of mass M which is at rest on a horizontal surface. The rod is given a slight ...
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0answers
238 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
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0answers
184 views
How to model an accelerometer measurements on a car wheel?
I am working on kinematically modelling an accelerometer on a car wheel.
When working on the initial conditions, I am confused whether or not I should use the gravitational acceleration since there ...
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0answers
299 views
Should angular momentum change or it should not.?
Let us consider a body with an arbitrary shape. Let its center of mass be assigned coordinates (o,o,z) with respect to an origin.Now let us consider two equal and opposite forces acting on the body ...
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0answers
166 views
Any interesting physics theroies/equations to be used in a video game? [closed]
I am designing a little game based on Newtons Graviational Law.
Are there any theories that I can use to create games?
thanks
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3answers
101 views
Why is $F = mg - T$ in this case?
The situation is as follows:
I am told that $F_{net} = mg - T$ in this case, but doesn't that not take into account that $T$ isn't applied to the center of mass? Newton's second law is defined for ...
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2answers
236 views
Force applied off center on an object
Assume there is a rigid body in deep space with mass $m$ and moment of inertia $I$. A force that varies with time, $F(t)$, is applied to the body off-center at a distance $r$ from its center of mass. ...
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3answers
72 views
Mass equals Moment of inertia when constant density?
I have found equation for moment of inertia $(J)$. I'm calculating $J$ for hemisphere, with rotational axis $Z$.
$$ J = \iiint\limits_V r^2 \cdot \rho \cdot dV $$
But if $\rho$ is constant ...
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1answer
291 views
Finding Rotational Kinetic Energy Of A Clock
The problem I am working on is:
"Big Ben, the Parliament tower clock in London, has an hour hand 2.70 m long with a mass of 300 kg, and a minute hand 4.20 m long with a mass of 100 kg (see figure ...
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2answers
261 views
Setting up equations for a Rotational Kinematics system
I'm having a hard time setting up equations for the following problem:
A green hoop with mass $m_h$ and radius $r_h$ m hangs from
a string that goes over a blue solid disk pulley with mass $m_d$
...
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1answer
87 views
Period of an Object in Periodic Motion
My attempt (if it matters):
The initial period is given by $T_X = \frac{2\pi X}{v}$ for some $v$.
The new period is given by $T_Y = \frac{2\pi Y}{v}$ for the same $v$.
$Y = \frac{X}{2}$, so ...
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2answers
1k views
Rotational kinetic energy during vertical circular motion of a particle
Why is it not necessary to take into account rotational kinetic energy when using the Law of Conservation of Mechanical Energy to solve vertical circular motion problems? After all, the particle is ...
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1answer
128 views
Relationship between the “angle of the floor” and the angular velocity in a banked turn?
Wel, imagine that you're in a carousel, and the floor is, let's say at $\theta=0$ so it's totally horizontal, if $\theta=90$ the floor would be vertically.
The object put above the floordoesn't move ...
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1answer
159 views
What causes a gyroscope to eventually rotate/fall over?
Hey so I've just learned about angular velocity and momentum and how torque changes it.
Looking at a wheel spinning around an axis, with one end being held up by a rope, what causes the wheel to ...
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1answer
84 views
How is torque equal to moment of inertia times angular acceleration divided by g?
How is the following relation true
$$\tau = \large\frac{I}{g} \times \alpha$$
where $\tau$ is torque,
$I$ is moment of inertia,
$g= 9.8ms^{-2}$,
and $\alpha=$ angular acceleration.
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1answer
44 views
Calculating the moment inertia for a circle with a point mass on its perimeter
I want to calculate the tensor of the moment of inertia. Consider this situation:
The dot represents a points mass, in size equal to $\frac{5}{4}m$. $m$ is the mass of the homogenous circle. I'm ...
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1answer
49 views
Finding the moment of inertia through superposition?
Let's say I have a body consisting of two homogenous spheres/balls that touch each other. I also have a body fixed coordinate system which consists of that body's principal axes. I know the the moment ...
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1answer
41 views
Rotational Dynamics
In studying rotational dynamics of a rigid body , I can't seem to understand why you can solve the problem correctly only using certain points in a body and not all ? Means angular momentum and torque ...
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2answers
70 views
What's the motion of this yoyo under external force will be?
A yoyo on a horizontal table is being pulled by a string to the right, the table is not frictionless. If we only know that the object doesn't slip, how do we know if the string is winding up or ...
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3answers
267 views
Aircraft Level Flight Trajectory
An aircraft climbs to 15000 feet and enters 'level flight' phase. My basic knowledge of physics says that forces on the aircraft at this time are balanced - as seen in this diagram.
...
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1answer
87 views
What happens at the end of Coriolis Deflection
Consider we launch a cannonball due south from a point at 45 degrees latitude in the Northern Hemisphere (e.g the point defined with the co-ordinate system on this diagram). The cannonball travels for ...
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2answers
2k views
Tensions And Pulleys With Masses
The problem I am working on is:
"A block of mass m1 = 1.80 kg and a block of mass m2 = 6.30 kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = 0.250 m ...
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1answer
111 views
Deducing latitude from Foucault Pendulum
Suppose I set up a Foucault pendulum and observe that it precesses at a rate of 216.528 degrees per day. While I am observing this, a total solar eclipse occurs. Where am I, and what is the date?
My ...
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3answers
2k views
Finding Angular Acceleration of rod given radius and angle
A uniform rod is 2.0 m long. The rod is pivoted about a horizontal, frictionless pin through one end. The rod is released from rest at an angle of 30° above the horizontal. What is the angular ...
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2answers
251 views
Precession of angular velocity about the body-fixed axis
My textbook mentions that under force-free motion of a symmetric top, its angular velocity vector $\overrightarrow \omega$ precesses about the $z$-axis of the body-fixed coordinate system. This seems ...
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2answers
492 views
How to interpret this vertical circular motion problem?
A bucket of water is tied to a rope and swung in a vertical circle.
The distance from the bucket centre to the axis of rotation is
$2.08m$. Calculate the angular velocity (in $rad s^{-1}$) of ...
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1answer
324 views
Calculation for force generated by a rotating rectangular blade
When trying to calculate the lift force generated by a simple rectangular blade, I've found the following equation: $$F = \omega^2 L^2 l\rho\sin^2\phi$$ in which $\omega$ is the angular velocity, $L$ ...
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1answer
178 views
Angular velocity $\omega$ by $v$
We have two girls, with mass (M). They become close to each other in speed of V. The distance between them is 3L.
I was asked to calclute the Angular velocity (w) of the two girls. So I set the ...
