The tendency of a force to rotate an object about an arbitrary axis.

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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 = ...
2
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1answer
455 views

Deriving torque from Euler-Lagrange equation

How could you derive an equation for the torque on a rotating (but not translating) rigid body from the Euler-Lagrange equation? As far as I know from my first class in Classical Mechanics, there is ...
2
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1answer
656 views

Normal force in a compound pendulum (physical pundulum) system?

Consider a compound pendulum pivoted about a fixed horizontal axis, illustrated by the force diagram on the right: # Okay, I can't figure out where the normal force on the pendlum should point ...
2
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1answer
556 views

acceleration of rings in aerotrim (human gyroscope)

I'm working on a graphic simulation (just for fun, for an open-source screensaver) of an Aerotrim - a "human gyroscope", one of those exercise/training machines with a human in the middle, perched on ...
2
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1answer
480 views

Why do people with bigger hands/wrists have bigger torque advantages in arm wrestling?

I have arm wrestled people with less strength than me who win simply because they have thicker wrists, or larger hands. It has nary to do with having better technique either, because their wrist size ...
2
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2answers
160 views

Why can't the units of work and torque be interchanged? [duplicate]

When I'm studying about work and torque, I found that their unit are the same. But, why don't we use Joule (unit of work) instead of Newton-meter (unit of torque)? Since $\mathrm{1\ Joule = 1\ Nm}$, ...
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2answers
183 views

Would box on the floor rotate?

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 ...
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1answer
82 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 ...
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2answers
216 views

Force and Torque Question on an isolated system [duplicate]

If there's a rigid rod in space, and you give some external force perpendicular to the rod at one of the ends for a short time, what happens? Specifically: What dependence does the moment of inertia ...
2
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1answer
130 views

How does the weight force distribute in roughly kite like kinematic to determine torques

I have a kinematic model like the simplified following image. Assume that all points are fixed. I'm interested in how the force $\vec{m}$ distributes across $a_2$ and $b_2$ up to $a_1$ and $b_1$. ...
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0answers
221 views

Why do control moment gyroscopes exhibit “torque amplification”?

There are a number of articles that describe the benefits of using control moment gyroscopes (CMGs) over reaction wheels in inertial navigation applications. One of the primary benefits of using a CMG ...
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3answers
193 views

Why if the torque equals zero measured from one point in space it equals zero measured from any other point?

I've heard it from two teachers and saw a task with a solution based on this assumption: If the net torque is zero when measured from one frame of reference, it is equal to zero in all other ...
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3answers
99 views

Deriving the law of moments

Recall the Law of Moments for a one dimensional rod: "When an object is in equilibrium the sum of the clockwise moments is equal to the sum of the anticlockwise moments." I understand that we ...
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3answers
437 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 ...
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2answers
1k views

How does a car's low gear increase power while going slower?

People have always told me that when a car goes into low gear, it goes slower but puts "more power" or "more torque" on the wheels, which allows it to descend slippery slopes or get out of mud traps ...
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3answers
1k views

Time period of torsion oscillation

For the oscillation of a torsion pendulum (a mechanical motion), the time period is given by $T=2\pi\sqrt{\frac{I}{C}}$ which is a result of the angular acceleration ...
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3answers
605 views

Self Balancing Unicycle

Here is a link to a video of a self-balencing unicycle. I'm curious as to how this works. In particular: What provides the torque to keep the rider from falling over? I know it's somehow provided by ...
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2answers
96 views

What fraction of peak horsepower do typical 4 door passenger vehicles use?

I was surprised when I looked at the power rating of the engine used on a Humvee. It's only ~190 horsepower, which is exceeded by many sedan engines. So an obvious question is why doesn't my Camry SE ...
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3answers
611 views

comparing torque and 0-60 speed in cars

Im looking a two cars, both are the same model but ones got a 2.0L turbo petrol engine and ones got a 3.0L turbo diesel engine. These are the full specs 2.0L Petrol 3.0L Diesel what im ...
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2answers
681 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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1answer
42 views

Torque in a heavy and light Body

Suppose we have two wheels attached to axis (each wheel has its own axis). One wheel is heavy compared to the other. The moment arm of force is same for the both wheels. A force F is applied on both ...
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1answer
222 views

Does mass concentration affect the torque induced by a force?

If you had two bodies with the same weight but one having mass concentrated more in the center, while the other had most mass concentrated on the outside, but both had the same center of mass and ...
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2answers
400 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. ...
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1answer
342 views

Finding the mass of bed/Patient

One of my friends has a problem and we don't know how to get this done, We want to to know the mass of a patient who is laying on a bed. One scales was put under the foot of a bed and weighed 232kg ...
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3answers
139 views

Chinook Helicopter Torque

The Chinook Helicopter has 2 rotors to counteract the torque generated by spinning the blade. Theoretically, could you use a smaller "back" rotor that is farther away from the main rotor to achieve ...
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1answer
285 views

Where I can find a torsional stiffness table for different types of stainless steels?

I am trying to comparing the torsional stiffness of different types of stainless steels. I googled the keywords but I could not find any useful information. Would anyone please give me some links ...
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1answer
114 views

Stability of balanced masses with different surface areas

Say I have this setup. The two round objects have equal mass and their centers of gravity at the same distance from the shaft. The objects only differ in that they have different surface areas ...
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2answers
161 views

Force acting on an object?

You have a bar of metal in an environment with no gravity. A force is applied on one end of it. How does it rotate? There is a non-zero torque on any random point selected on the bar. For example, ...
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1answer
254 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) ...
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1answer
171 views

How to sum several thrust vector on a single object (like a plane)

I'm a developer. I tried (mostly for fun) to create a realistic physic engine. I try to sum all forces (here thrust) applying to an object in two composantes: an acceleration vector and the angular ...
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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 ...
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1answer
68 views

If a cart hits a wall, does the weight of it affect how it moves, when the center of gravity is constant?

I have a model that represents a bicycle (a wood block with wheels), and I'm balancing the center of gravity so it's the same as a real bike. However, when the center of mass is kept constant, does ...
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1answer
869 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 ...
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0answers
17 views

What will be the direction of the force required on the ball to move the ball up the stairs?

Is this diagram correct? The point of force A is at the farthest distance from the fixed centre O ,so the moment arm CD is greater and therefore,maximum torque would be produced.Is my concept ...
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0answers
34 views

How does a simple weighing balance actually work? [duplicate]

I have made a simple sketch of how I think the system looks like. My problem is: I always thought that the angle the balance makes is a function of the difference between the two masses (or the ...
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1answer
33 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 ...
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0answers
45 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 ...
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1answer
58 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 ...
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1answer
167 views

Newton's second law for rotation

Can the second law of motion for rotation, $\vec{\tau}=I \vec{\alpha}$, be used for any axis? Is there any case that acceleration $\vec{\alpha}$ is not in the direction of applied torque ...
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0answers
33 views

Help with inductance and a moving (rolling) rail problem

I can't even do the first part. I've exhausted just about every direction. I've done plenty of moving rail problems without rolling, but I'm guessing you have to have some relationship between the ...
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0answers
94 views

How to measure the energy required to pedal an exercise bike

I have hacked a FitDesk exercise bike to output the RPM of the pedals and the position of the resistance control within its range of travel. I want to characterize the energy that is required to ...
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1answer
186 views

Arduino Servo Torque Calculation for a Automated Telescope

I have a class project where I am using several servos to control a telescope. I'm trying to figure out the torque needed to rotate the tilt of the telescope with a servo from 0 to 90 degrees. I ...
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176 views

Angular Momentum Conservation in Gravitational Interaction

thanks for any help. I'm trying to show that in a 2body problem, angular momentum is conserved given that $\dfrac{dp}{dt}=\dfrac{-GMm(rv)}{r³}$, where p is momentum, t time, G gravitational constant, ...
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463 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 ...
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1answer
140 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, ...
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56 views

Two impulses on body

Say I have a physics simulation with a single body with three degrees of freedom (two axis and rotation). I have two impulses of equal magnitude in opposite directions. When applying these impulses in ...
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0answers
216 views

Torque, lever and mass

The Force used in a catapult is exerted near its axis. If we double the length of the arm of the catapult, but still use the same Force at the same point as before near the same axis, does the ...
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0answers
70 views

Truck driven from a small motor that can carry a heavy load, yet can travel fast.

I am building a truck from trash as materials. I have one small motor and a a few small gears, but no other engineered materials are allowed. The truck must carry a load for a distance of 3m. The ...
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0answers
170 views

How much force is required to hold an umbrella?

Assuming a small umbrella (e.g. http://www.amazon.com/ShedRain-WindPro-Umbrella-Close-Size/dp/B001DL5WN0). What are the factors that need to be considered? I assume where I hold the umbrella might ...
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0answers
601 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. ...