# Tag Info

Accepted

### Are there torques affecting Earth?

Earth Rotation Variations from Hours to Centuries (Dickey) has some analysis of these variations and states that they are mainly due to interactions with the atmosphere and with the earth's core. ...

### Is projection of a simple pendulum, doing SHM as well?

A simple pendulum does approximate shm. Suppose that we displace it through angle $\theta$ from its equilibrium position. If $s$ is its displacement along the arc from its equilibrium position, then ...

### Static friction when rolling with constant speed

The torque causes a force $\tau = rF$ on the contact point of the wheel No. The torque isn't creating any forces on the wheel. On a frictionless surface, the wheel would rotate but no linear ...

### Has a heavier atmosphere and the relocation of oil around the Earth had a measurable effect on the rotation of the Earth?

The effect is minuscule, because: Oil and gas and coal do not come from "the center of the Earth", they come from relatively close to the surface. The deepest oil wells in existence are &...
Accepted

### Moment of inertia of a rolling cylinder

The formula $I=\frac{1}{2}mr^2$ for the moment of inertia of a solid cylinder is only valid, if its density is homogeneous. But it is not valid anymore, if the density varies with radius. For example: ...

### How to mathmematically direction of friction of spool?

With friction, the bottom doesn't slide. It matches the speed of the table, which is $0$. The spool rolls. Suppose the spool was sitting on ice, so F was the only force. How would the spool accelerate?...

### Static friction when rolling with constant speed

1 There are static frictional forces between the tyre and the ground: static frictional force on tyre due to ground, and static frictional force on ground due to tyre. The first of these two static ...

### How does the Dzhanibekov Effect change if replaced with a propeller?

A T-handle has three distinct mass moment of inertia values (indicated below in red, green and blue directions) As you notice, about the z-axis (blue) the MMOI value of $47\;{\rm kg}\,{\rm mm}^2$ is ...

### Static friction when rolling with constant speed

Different contact points So, I am not entirely sure what other answers you have gotten, but I will say that in my own case, when I was trying to learn about friction on wheels, one of the most ...
1 vote

### Multiplying a force vector by rotated unit vector produces strange results

Please define what $*$ is in $v_3 = F * v_1$ You need to take the dot product, and not any quaternion product or other product. The reason I suspect you did not, is because the result isn't along the ...
1 vote

1 vote

### Is Joule equivalent to Joule/radian?

A radian has no physical dimension, it's a pure number. So, if you do dimensional analysis, \begin{equation} \dfrac{[torque]}{[angle]} = \dfrac{[torque]}{1} = [torque] \ . \end{equation} Recalling ...
1 vote

### Doubts about the parallel-axis theorem

Consider a body orbiting at some distance around a fixed point and spinning about its center of mass (such that both rotations are in the same plane). The orbital angular momentum will be that of a ...
1 vote
Accepted

### Vanishing of angular momentum with scale

… the whole universe doesn't possess an angular momentum. It can't: If it had one, the centre would be a special point (which isn't allowed) and the velocities of the outer regions would easily become ...
1 vote

### A pure rolling sphere problem

Initially centre of mass was not at rest. Since it was moving with a constant velocity, it will continue to do so. Since no force acts (friction wasn't there before because pure rolling was already ...

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