-1
votes
0answers
24 views

How do I know which force to use in moments calculation?

I'm working on some Statics problem, with the method of joints, etc and for all of them, we use sum of moments = 0. However, I'm very confused about which forces I should use to find the sum of ...
1
vote
1answer
43 views

Torque due to Gravity

I have learned that a torque on an object due to the gravity can be calculated as if the gravity acts on the center of mass of the object when the object is near the surface of the earth. Now I want ...
0
votes
3answers
28 views

Converting moment of inertia (kg per square m) to torque or moment of force (in/lb or n/m) [closed]

My problem is that I have an dc starter generater and they say that to test it I must have a flywheel that can provide the starting inertia of .522 kg per square meter. What I need to know what will ...
0
votes
1answer
61 views

Work done by magnetic field on magnetic dipole

In the above slide, it reads that $W=\int\mu B sin(\theta)d\theta=\mu B cos(\theta)$. But, I thought that $\int\mu B sin(\theta)d\theta=-\mu B cos(\theta)$ by some calculus calculation. Can ...
1
vote
1answer
71 views

How much wind does it take to tip a sign over? [closed]

Or said another way - how much counterweight does the base of a sign need to keep it from tipping over given a specific max wind? Assume the sign does not let wind through Assume the base of the ...
0
votes
0answers
26 views

Wikipedia's derivation of torque related to angular acceleration [duplicate]

Wikipedia derivation of the relationship between a torque and an angular acceleration is given here. Could someone help me to see how the following: $$\vec{\tau} = \left(-\sum^n_{i=1}m_i [\Delta ...
1
vote
2answers
90 views

Why neglect friction when computing torque?

There is a block of wood on a plank, with friction, and the block is moving down with uniform speed. They are asking what is the torque acting through the center of the block. My doubt is that ...
0
votes
1answer
40 views

Coordinate System vs. Angular Properties vs. Centroid

Please help me check my understanding related to the rotational motion of a 3D rigid body after reading some Physics textbooks and googling for some more materials (e.g., Wikipedia's Torque, ...
1
vote
1answer
40 views

Have I calculated the Newtonmeter ($Nm$) of torque for my corded drill correctly? [closed]

The corded drill is rated at: 450watts at 3000rpm the calculation I have used is: $$\frac{450}{3000} \times 2 \times \frac{3.14}{60}=0.0157 $$ I feel I have made a basic error somewhere (as the ...
1
vote
0answers
61 views

Rolling in 3D using Torque, Angular Momentum/Velocity

I'm stuggling to get a simulation working correctly. Below you can see what I am attempting to do. You can also view it here. Can you spot where I'm going wrong? (Calculated at start) 1) Inertia ...
2
votes
1answer
203 views

Line of action force

The task is to reduce the two forces into a single net force and then find the equation of its line of action. I chose to find the net force and momentum with respect to the origin. The magnitude of ...
0
votes
1answer
90 views

Moment around a point in a frame

Note: Both diagrams are 2d(they might look 3d because I drew them manually.) I have a prismatic frame that looks like this: I made a section on the half of the first pillar(the red line represents the ...
0
votes
2answers
74 views

Mathematically determining the direction of torque?

I need to mathematically derive the direction of torque in a 2D plane(clockwise/anticlockwise), for a physics engine. I have torque calculated, but it is always positive, so rotation always is in the ...
2
votes
3answers
1k views

Force applied to wheel in pure rolling motion at contact point with road

Suppose a wheel with radius $R$ is resting on a non-inclined surface. A torque $\tau$ is applied to the wheel center. In an attempt to prevent wheel from spinning, the ground applies a static friction ...
-4
votes
0answers
53 views

maths question on levers [closed]

Someone holds a 2kg weight in their hand at a distance of 35cm from the elbow (fulcrum) and the downward force (load) due to the weight is 20 Newtons. Calculate the effort in Newtons that the ...
2
votes
1answer
144 views

What forces are exerted on a clothespin in space?

Let's say a clothespin is modeled as a simple torsion spring as follows. Given: $p_1,\ p_2,\ p_3$: point-like objects of equal mass in 2-D space. All objects float in space, i.e. the center of mass ...
0
votes
1answer
163 views

Net torque on an object

Suppose that a cord is wrapped around the rim a disk of radius $R$. The disk is allowed to rotate around its central axis (the line passing through the center and perpendicular to the disk surface). ...
0
votes
0answers
33 views

Gyrocompas equation

Ok, need a little help for part (b) of the following problem. I set my axis similar to figure 113 and have expressed both $\omega$ and $\Omega$ in terms of the new coordinates. I have been told to ...
1
vote
1answer
344 views

Calculating torque in 3D?

Say you have a sphere, and you have several torque vectors acting on it, all at different points. Say you have the vector (6i + 3j + 5k) originating from point A, and the vector (3i + 1j + 9k) ...
0
votes
0answers
100 views

Correct way to calculate torque produced by axle

For my electrical engineering course, we had to build a simple DC motor that can lift a coin. I have tested the motor, and here are the results: rotational speed (no load): 3630 RPM (380 rad/sec) ...
2
votes
2answers
246 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
0
votes
2answers
440 views

Equilibrium of Force Systems including Torque

please help me to solve this problem.. this is only the #3 on my homework and the only thing i didn't know here is how to calculate the tension T. please teach me how to solve the tension here ...
1
vote
0answers
645 views

Torque of a winch with pulleys [closed]

I'm working on a project that involves using a remote-controlled electric winch to raise and lower my bicycle using a pulley system. The problem is that I don't know how much torque will be required ...
1
vote
1answer
147 views

Torque on a Box

I think I'm missing something with torques. I seem to have gotten myself confused. I have a box that's centered at ( 0 , 0 , 0 ) with length ( $x$ dimension ) = 1 , width ( $y$ dimension ) = 0.25, ...
0
votes
3answers
287 views

Calculating the torque at a point when a motor is stopped?

So, I'm trying to solve for the torque $\tau_A$ of a motor. I have attached a strong stick to the motor, like so: I apply a force $F$ on the stick which stops the motor. The distance from the ...
2
votes
2answers
268 views

Basic Torque: Did TA get it wrong?

The question itself: A modern art sculptor anchors 1 meter of a cast iron pole in the ground and leaves 3 meters of the pole sticking out of the ground at a 60° angle. The owner of the metal shop ...
0
votes
1answer
282 views

Confusion in connected pulleys problem

I'm having some troubles in understanding why my reasoning doesn't work in the following problem: Problem Two pulleys of mass $m_1$,$m_2$ and radius $r_1,r_2$ are connected by a belt (like chain ...
0
votes
1answer
464 views

Calculating torque with gears and wheel-axles

For my homework in engineering, I was given a question like this: There is an axle attached to a gear, which is meshed with another gear, which has an axle attached to it. I am given the diameter of ...
0
votes
2answers
149 views

Is my physics correct or torque correct?

I would like to put this into a differential equation. This is what I have. $$r \times F = I \ddot\theta + \mu \dot\theta + k \theta$$ What I need verified: $\text{Torque} = I\ddot\theta + \mu ...
1
vote
3answers
496 views

Maximum angular velocity to stop in one rotation with a known torque

I have an object I can rotate with a given torque. I would like to stop applying torque once I've reached a defined maximum rotational speed. The maximum rotational speed should be defined so that ...
2
votes
1answer
84 views

Summing moments, where have I gone wrong?

Because I don't have enough rep to post images, the question is question 3 part iii) from here: http://www.mei.org.uk/files/papers/m209ju_jk32.pdf The surface at the contact point B is rough. The ...
0
votes
1answer
2k 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.
0
votes
1answer
76 views

Pendulum system: how is derived the output as Energy?

Good day to everyone, I want to understand in which way the "Energy equation" is been implemented to this pendulum system. $x_1(t)$: The angular position of the mass $x_2(t)$: The angular velocity ...
0
votes
1answer
149 views

Find the bending moment of a pole attached to a moving block

I'm having trouble with the following problem. What I've done so far: x-y is the usual coordinate system. $a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$. To ...
0
votes
1answer
411 views

Direction of the torque

In each one of the following figures there's a pole of length $1.2 \text{m}$ and there's a force $\vec F = 150 \text{N}$ acting on it. Determine the torque that is created by the force relative ...
1
vote
1answer
2k views

Calculating the acceleration of a car

I'm trying to calculate the maximum acceleration a car can achieve with the current gear ratio. I am ignoring drag forces and friction to keep it simple. I'm doing this by: calculating the torque ...
1
vote
0answers
638 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. ...
0
votes
1answer
279 views

How can the torque a bicycle experiences be calculated based on the center of gravity, weight and a force?

The position center of gravity of a bicycle and its rider is known, and the distance from it to the point of contact of the front wheel with the ground, in terms of horizontal and vertical distance (x ...
0
votes
0answers
348 views

How do you determine the torque caused by the mass of a lever?

Suppose we have two objects sitting on two side of a lever, and the lever also has a mass, and those objects have masses. Then how we can balance $\sum τ$? This is what I have done: ...
1
vote
2answers
784 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. ...
0
votes
1answer
446 views

Calculating torque in a structure

I posted this on math stack exchange but realize it is more a physics question. I have a structure which is set up as shown in the image. A weight hangs from point A with mass $m$. Joint B is free ...
2
votes
3answers
3k views

Proving angular momentum is conserved for a particle moving in a central force field $\vec F =\phi(r) \vec r$

A problem I am trying to work out is as follows: A particle moves in a force field given by $\vec F =\phi(r) \vec r$. Prove that the angular momentum of the particle about the origin is constant. ...
0
votes
1answer
509 views

Can anyone solve this simple static equilibrium problem? [closed]

A bridge is 50m long, has a mass of 20,000kg, and rests on two pivots, A and B. The distance between A and the left side of the bridge is 10m. The distance between B and the right side of the bridge ...
1
vote
1answer
897 views

Gravitational torque about a bolt that a mass is hanging from [closed]

A uniform rectangle sign h=20.0cm high and w=11.0cm wide loses three of its four support bolts(at points p_1, P_3, and p_4) and rotates into the position as shown, with p_1 directly over p_3. It is ...
0
votes
2answers
380 views

Finding work done by rotational force?

A disk with a rotational inertia of 5.0 kg·m2 and a radius of 0.25 m rotates on a fixed axis perpendicular to the disk and through its center. A force of 2.0 N is applied tangentially to the ...
1
vote
2answers
423 views

How do you choose the locations of forces when calculating moments?

A uniform bridge of weight 1200kN and of length 17m rests on supports at each end which are 1m wide. A stationary lorry of weight 60kN has it’s centre of mass 3.0m from the centre of the bridge. ...
0
votes
1answer
380 views

if a force is 1 newton metre, what is it at 2 meters?

If I have a force, say 24 kg/cm what would that equate to at 2cm? I would like to know the formulae for calculating this. For example. If a motor can hold an object of 24kg at 1cm from its pivot ...
2
votes
3answers
1k views

Torque homework

We have learned that Torque is equal to a force that is perpendicular to a radius (displacement); however, I just cannot grasp one of the study questions we received: A hammer thrower accelerates ...