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All Questions

2
votes
3answers
78 views

Can a tilted wheel roll straight?

The common explanation of why a wheel that is falling to one side will turn towards that side to balance itself is gyroscopic precession, i.e. the torque produced by the falling of the wheel plus the ...
0
votes
0answers
33 views

Forces on a Rotating Rigid Body

This question has been puzzling me for some days now and I thought I might ask you guys for some help. Say that we have a rigid body (like a rod) that is in a vacuum in space. Furthermore, say that ...
0
votes
2answers
205 views

Torque, Angular Acceleration and Linear Acceleration

We know that we torque is applied, it cause an angular acceleration in the rotating body similar to what a force does to a body moving on a straight line. But my question is, Does Torque affect the ...
1
vote
0answers
57 views

Does the hinge reaction do any work?

I was doing some questions in rotational mechanics and I am not able to understand the concept behind hinge reaction which acts on a rod suspended at a point. I am taking a simple example here. Let's ...
1
vote
1answer
60 views

Perpendicular weight force on an object that is tipping over [closed]

I'm currently working on a problem I can't seem to find an answer to. I have an object that is hanging over a cliff. This object is exactly 12m in length, and it starts off in equilibrium (6m over the ...
2
votes
3answers
101 views

Why do vehicles with a higher center of mass roll more easily considering that they have a higher moment of inertia?

It is a well known fact that cars with a higher center of mass roll over more easily, but why is this true considering that higher center of mass = higher moment of inertia? I understand that the ...
6
votes
3answers
1k views

Why do things spin?

Let's say I have 2 boxes, one of mass M and one of mass 2M. They are separated by a distance of 1 meter. I drop them from the same height and see that due to the earth's gravity, they accelerate at ...
-1
votes
1answer
39 views

relation between input and output torques for a geared machine

what is the torque in both ends of this gear set ? thanks! Multiple speed gear paradox box https://www.youtube.com/watch?v=bIMDtkm_ENQ
1
vote
0answers
62 views

Transverse speed of hamster in wheel as function of theta

i need help with conceptual understanding of how this system works. A small animal is running in a wheel with radius R, (and 0 mass). When the animal is at an angle $\theta = \alpha $ measured from ...
-1
votes
1answer
29 views

Direction of torque in this situation [closed]

Suppose a body is rotating with uniform speed i.e. dv/dt=0(all the drags and frictions are zero) then what will be the direction of torque or will it actually exist?since the only force is acting ...
5
votes
3answers
141 views

Why does it get harder with time, to rotate a screw with a screwdriver?

A couple of forces act on the machine screw and create the turning effect. But after sometime it gets harder. So, net torque is decreasing, but why is it decreasing? Frictional force comes into action,...
-1
votes
1answer
312 views

Pulley system with gear - torque

I would like to ask, how can I calculate torque required for motor in this system if: input pulley is smaller one (number of teeth= z1) output is larger one (number of teeth= z2) with pinion (modul= ...
0
votes
2answers
1k views

Calculating acceleration, etc. of a gear train with multiple driven gears

I'm writing a basic gear train simulation, where it is possible for every gear to be attached to a source of torque/angular friction. All the online resources I've found only deal with systems where a ...
0
votes
1answer
850 views

What is the purpose of torque in projectile motion?

Torque, $\tau$ is defined as: $$\vec{{\tau}} = \vec{r}\times\vec{F}$$ Intuitively, it's the rotational effect of force. However, using the above definition of torque we can calculate the torque ...
4
votes
1answer
975 views

How long does it take a rolling ball to stop?

I am confused by a problem that appears to have two separate, valid solutions which contradict each other. Let's say we take a thin disk, prop it up, give it an initial push, and then watch it travel ...
2
votes
5answers
2k views

Given torque, what is the direction of motion?

Torque is the cross product $\vec \tau = \vec r \times \vec F$, which means it is perpendicular to both $\vec r$ and $\vec F$. Consider some essentially two-dimension problem, like a horizontal iron ...
1
vote
1answer
1k views

When does torque equal to moment of inertia times the angular acceleration?

When does torque equal to moment of inertia times the angular acceleration ? Particularly, for example, if a disc is rotating and translating on a horizontal surface with friction by the help of ...
7
votes
5answers
2k views

How to choose origin in rotational problems to calculate torque?

We know that $\text{Torque} = r \times F$ and $r$ is the position vector. But the position vector depends on the choice of the coordinate system and in turn on the choice of origin. So, where should ...
0
votes
1answer
21 views

Stopping rotation within a specific amount of spins

I have a disc spinning with a known angular velocity $\omega_o$. I have to make it stop in exactly $N$ spins using a torque ecuation that looks like this : $$\tau(t) = -B·t$$ Which is the correct ...
1
vote
1answer
379 views

Why will kinetic energy decrease?

Specific situation : A ring of mass M and radius R is rotating about its axis with angular velocity w. Two identical bodies each of mass m are now gently attached at the two ends of a diameter of the ...
1
vote
0answers
796 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
4k 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 ...
0
votes
2answers
7k views

Torque and Pulleys [closed]

I have the solution to the problem below, however I approached the question differently than my professor and I do not understand why my answer is different. Can someone help explain where I'm going ...
2
votes
0answers
738 views

Maximum friction force for a wheel to be able to roll

The wheel with mass $M$ and radius $R$ below is free in space (it is not on the ground). A torque $\tau$ is applied to it through an engine. A horizontal force $F = \frac{\tau}{R}$ is also applied to ...
1
vote
1answer
629 views

How does ground interact with a box rotating around its corner?

I have some questions about how forces $F$, friction force $F_{friction}$, and normal $N$ interact in order to the box below to turn (clockwise) about the red corner, without sliding. The force $F$ is ...
0
votes
0answers
27 views

Is it possible to impart a moment with soundwaves?

How can one adjust the properties of a sound wave to use it to spin an arbitrary object of shape S in a medium comprised of the same material. My intuition tells me that it would be much more ...
2
votes
1answer
3k 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.