What is Arm: Definition and 215 Discussions

In human anatomy, the arm is the part of the upper limb between the glenohumeral joint (shoulder joint) and the elbow joint. In common usage, the arm extends through the hand. It can be divided into the upper arm, which extends from the shoulder to the elbow, the forearm which extends from the elbow to the hand, and the hand. Anatomically the shoulder girdle with bones and corresponding muscles is by definition a part of the arm. The Latin term brachium may refer to either the arm as a whole or to the upper arm on its own.

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  1. Fury22

    B Lever balancing physics (video game design)

    Hi everyone! I am not a physicist or a physics student. Just a simple video game programmer. I have recently gotten into a discussion with my fellow programmer about a specific hypothetical problem regarding levers. The problem might seem very simple at first, but cause me a bit of headache...
  2. jkengineer

    High School Project - Mini Airhockey Table with Robotic Arm

    [Mentor Note -- This thread start is outside of the normal scope of PF, but we are allowing it because it's a pretty well-done project for the level of the student] :smile: Hi all, I would like to share my high school engineering project - A Mini Airhockey table with Robotic Defender...
  3. Dex_

    Apple's new ARM CPUs vs, classic x86 for physics?

    Hi it's my first post here! I'm in my second year of my degree and looking to replace my computer. The new M-series chips seem like a better deal, however I am nervous that some software that might not be compatible with the ARM architecture. For more context on my workflow I do quite a bit of...
  4. kamalMKA

    Mechanics for High School Students: Building a Robotic Arm

    TL;DR Summary: Mechanical engineering,robotics,mechnics,dynamics Hi guys , I'm new to mechnics and I want to learn it for building robotic arm , but I find mechanics book topics somewhat difficult for me , what I need to learn to get started as I'm a highschool student with basic level math.
  5. core7916

    C/C++ Trouble programming Arm Cortex M0 (stuck in the reset_handler)

    Hello, i am programming pga970evm module and the core is of arm cortex m0. the program what i have is building succesfully , but while debugging it is stuck or halting in reset (reset_handler) and not comming out of it (startup code). i will provide screen shot of debug page. another thing is...
  6. Spocktastic

    Trying to Figure out Tension force angle on Arm

    I already solved for part a, setting the sum of the Torques of the arms and deltoid equal to 0 and subbing in values which lead to a tension force of 870N in the deltoid. For part b, I remembered the law of static equilibrium, so the summation x and y components of all the forces in the system...
  7. T

    How to calculate the speed of this umbrella extension arm?

    TL;DR Summary: Have a university project where we are calculating the speed of the arm at the end. I need some help on where to start on the calculations. We have tried to determine instantaneous center of rotation for the device. We want to find the linear velocioty of point B. There is a...
  8. D

    Resultant pedal force (FRESULTANT) Force tangential to the crank arm

    %% part 1 clear all; close all; clc; torq_crPK = zeros(10,1); ang_tqPK = zeros(10,1); ang_powPK = zeros(10,1); torq_crDS = zeros(10,1); torq_crUS = zeros(10,1); WD = zeros(10,1); WDpos = zeros(10,1); WDneg = zeros(10,1);%% INPUT VARIABLES for i=1:10 % cyclist number % read in the...
  9. wyattmarshall

    Best way to self-teach Electrical Engineering and Embedded Systems?

    Summary: Trying to self-teach Electrical Engineering, Embedded Linux and AVR/ARM to make a career change into embedded systems development and I need suggestions on the best way to do that. I have a plan but I honestly have no idea if its a good one. I have been into computers my whole life...
  10. K

    The effect of slightly slanted distance (arm) on torque output

    Hi everyone. In most cases when torque and lever arm are being discussed, it is the angle between the force and the arm that matters (like in the following picture). However, non of the articles that I have read so far have mentioned anything about the distance between force and fastener being...
  11. greg_rack

    Analyzing a Combination of Beer+Lower Arm for Maximum Acceleration

    Hello guys, to analyse the above-described situation I have opted for considering the body "beer+lower arm" as a whole, therefore computing the new position of the COM for the correct FBD and equations of motion. With some uncertainty on the statement of the problem, I have interpreted the...
  12. M

    Engineering Statics project involving shear & moment diagram of a control arm

    Part of a project I am working on (part #3…see description below) is asking us to find the internal loads (shear and moment) and draw the corresponding shear/moment diagrams of the control arm shown below. It’s a little tricky to me, because all of the members associated with these type of...
  13. rudransh verma

    Displacement of clock arm

    I calculated the angle as 225 whereas answer says something else.
  14. Poetria

    How can we interpret the inverse matrix of a robot's arm?

    If I understand this correctly, this is the right answer: ##M \begin{pmatrix} 0.2\\ 0.1\end{pmatrix}## There is an inverse matrix in the next question: Continuing with the previous problem, let ##\vec v = M^{-1} \begin{pmatrix} 0.2\\ 0.1\end{pmatrix}##, where ##M^{-1}## is the inverse matrix of...
  15. M

    Engineering Rotation around fixed axis (robot arm), dynamics

    Hello, Given the figure below, and the following statement: "The robot arm is driven by two hydraulic cilinders A and B which brings point D rotates CW. The gear in point D has a angular velocity of 5 rad/s. Calculate the velocity and acceleration of the part in point C." First I determined...
  16. DaveC426913

    Designing a Tapered Scissor Arm: Challenges & Solutions

    This is what I am calling an extensible scissor arm: This one is symmetrical - the same breadth along this entire length. I'd like to design one that narrows from one end to the other. I realize that will change the geometry of each section - they will get shorter and shorter - but is it...
  17. MattGeo

    Torque and Moment of Inertia of a Lever Arm

    I never really considered this back when I was taking physics in college but imagine for the sake of thought experiment that you have an extremely and impractically long wrench and it is fixed to the bolt you wish to tighten. Now the longer the lever arm the greater the torque so if you double...
  18. R

    B LIGO Arm Length & Sensitivity: What's the Relation?

    [Moderator's note: Spun off from previous thread due to new question.] I have read here: http://backreaction.blogspot.com/2016/02/everything-you-need-to-know-about.html?m=1 That there is a proportionality between the size of LIGO arms and the wavelength of gravitational waves that it can...
  19. Y

    Engineering Equation for a DC motor driving an arm

    https://d2vlcm61l7u1fs.cloudfront.net/media%2F9b2%2F9b24aa39-e135-4529-9eaf-29a3cd057502%2FphpubWKNH.png
  20. Leo Liu

    Is the length of the arm r in a polar coordinate a function of the angle?

    My textbook says ##\vec r (\theta) = r \hat r (\theta)##, where ##\hat r (\theta)## is the terminal arm (a position vector in some sense). It can be seen that both ##\vec r (\theta)## and ##\hat r (\theta) ## are function of ##\theta##; whereas, the length of the vector ##r## is not. I...
  21. K

    Force required to lift an arm

    Hi, Hope one of you might be able to help me with some calculations :) I'm trying to calculate the amount of force required to lift an arm, based on weight, distances and angles. I made a sketch to illustrate my problem. where: Lac = Length of arm Lab = Distance from "anker-point" to...
  22. D

    Finding the torque of a robotic arm

    let's say we have a robotic arm, connected to a servo motor. the servo motor is rated at 500 kilogram-centimeter. the robotic arm lifts something upwards. will the torque remain constant? if so, torque equals force times distance to point of application of force time sine angle, will the angle...
  23. T

    Crane Arm Model using beam theory

    Can a Bernoulli or Timoshenko model be reasonable for a crane arm, on ships? Yes, the arm might have a truss element, yes there is a hydraulic force to lift the arm (or cables). But to some extent, can one model the crane arm as one of a simple beam (either Timoshenko or Bernoulli -- and...
  24. jisbon

    Free body diagram -- Ball rotating on one arm of a Y shaped pole

    To start off with, I can't seem to interpret the FBD here. Here are my drawing: and what I interpret as. From here, I feel like I can (it's wrong obviously but I'm not sure why) state that sin theta = o/h = o/mg = N/mg , so N= mg sin theta? Thanks
  25. Like Tony Stark

    Finding the angular velocity of a rotating arm

    A) The slider experiments three forces, all of them are on the ##x## axis (considering ##x## axis as the axis aligned with the arm): Normal force (exerted by the support), elastic force and centrifugal force, which is ##m.(\omega^2 r)## Elastic force is equal to ##Fe=-k \delta =-2 (R-2R)=2R##...
  26. A

    Compound lever arm - compressor design

    So what comes to mind is utilising the full height and further node points in a triangulated system... however being only just now introduced to the concept of a compound lever I am unsure of how to get this system to work. Any thoughts much appreciated.
  27. YoungPhysicist

    Wood/Glass/Metal Wooden hydraulic mechanical arm

    Yesterday, I found a device in the recycle bin of our school’s art classroom. It’s a broken wooden hydraulic mech arm someone built a couple years ago. After some fixing and filling the syringes with water again, this is how it looks now: Here’s a video of it working: I am aware of...
  28. brotherbobby

    Understanding Torque: How Balancing a Dumbbell Changes the Difficulty

    The figure above shows a man holding the dumbbell in the two different positions. The force ##F ( = w)## that the man has to apply is the same in both cases. So really, the two cases should be as easy or as hard. However, in the second case, the man has to balance the torque that the dumbell...
  29. M

    Calculate the Angular Velocity of an Arm from a Data Set

    Hi, a newbie to the site and hoping someone can help. Its been a long time since I studied physics or math at school. I am having some difficulty calculating the angular velocity of the arm trhough a partial movement (phase). The data set I have separates the angular velocity into the three...
  30. J

    Pusher Arm Torque Calculation

    Hello All, I am designing a pusher arm for a project (Please refer attached picture), I need to calculate required torque to select a rotary cylinder. The arm is mounted on a rotary cylinder and it has a dead plate underneath. I understand we can calculate torque= Mass moment of Inertia x...
  31. T

    Force applied to lever arm to twist foot pound torque

    If i need 1000 foot pound torque of 1000 foot pounds twisted very easily How long should the lever arm be and and how much force at the end of lever arm is required ? Tony Singh
  32. T

    Automotive Calculating geometry for single pivot arm

    Hi, Guys, I am building light electric vehicle for fun and hobby. I am experimenting with stuff, but have some difficulty calculating a reasonable geometry for the suspension. It is a SINGLE arm suspension and I am planing to use Fox Float Air Shock with length 190mm, it has pressure control...
  33. RodriRego

    Inverse Kinematics of a 6 DOF Robotic Arm

    Homework Statement Hello. My colleague and I have been struggling with this assignment where we have to: - Given the position and orientation of the end-effector of a robotic arm with 6 degrees of freedom get the joint angle values (inverse kinematics). The robotic arm in question is the...
  34. D

    Net Torque on an Angled Arm

    Homework Statement My teacher gave us a solution of + 1250 Nm Where CCW = positive torque I know that the torque of the 600N + 300N forces + 1250Nm = the torque of the 500N force. I can't figure out what angles work with the forces at the end of the pipe. Homework Equations Σ T = 1250 Nm T...
  35. S

    Mounting Arm Torque for Short Throw Projectors on Different Walls

    Hi there, I'm going to install same kind of short throw projector in multiple locations, with different wall materials. Projector has integrated wall mount arm (see picture). - How to calculate total torque affecting mounting plate top row screws? Some locations have plasterboard walls...
  36. CaptainAmerica17

    Electronics Best way to scavenge parts for a robotic arm?

    I'm a bit new to DIY robotics and for one of my first projects, I want to build a robotic arm. I'm still thinking out the plan for it, but I'm going to need to start gathering parts. Does anyone know of the best way to get parts if you don't have immediate access to a 3D printer? Does anyone go...
  37. M

    How to measure arm trajectory?

    I am not sure in which section this question should belong so I am placing it here for now. I have no experience in physics and body motion so appreciate some patience with my question. the information i have are pixel coordinates of the head, shoulder, elbow, hand, knee, hips and leg of 2...
  38. Beth N

    Equilibrium of Rigid Bodies. Rafter. What is moment arm?

    Homework Statement Two uniform 150 N rafters rest on frictionless floor, held together by a rope. A 500 N load is held at their apex. Find tension in the tie rope. Homework Equations ##torque= rFsin \theta =Force*Moment Arm ## The Attempt at a Solution The angle ##\theta## in the picture...
  39. I

    Force Calculation -- Hydraulic cylinder and a rotating arm

    Hi There, Long time reader, first time poster.. I hope someone out there can help me. I'm designing an add-on to an existing piece of equipment and I'm unsure of how to calculate the resultant force output from a hydraulic cylinder. On a straight push, the chosen hydraulic cylinder has an...
  40. Dreezy

    I Help creating a coordinate system for a robotic arm

    Hey guys, I would appreciate some help with the math behind creating a working coordinate system for a robotic arm. I am currently trying to determine what servo angles are necessary to align a robotic arm's claw to the given coordinates. Geometrically simplified, the robotic arm is a...
  41. SilverJW

    I Designing Rehabilitation Equipment for an Upper Limb (arm)

    Before I ask my question, here's a little introduction of myself. I am a college student studying in Bioengineering, so I've been tasked to create an equipment to help rehabilitation for upper limb (any point of the upper limb, doesn't have to be the entire upper limb). So I have this initial...
  42. P

    Moment Arm: Determine Torque Vector & Qty

    Homework Statement I'm trying to determine the torque vector and quantity of said vector per the sketch attached. Homework Equations T=fd[/B] The Attempt at a Solution T = 100 lbs x 2 f2f T= 200 ftlbs But my real question is where is that Force being applied at is it the attachment point...
  43. Brandon Preble

    Trebuchet Throwing Arm Optimization

    Summary: Some help would be greatly appreciated for finding the ideal taper and x/y dimensions of a trebuchet throwing arm to optimize strength and minimize the moment of inertia. Long Version: I am a high school junior currently in the process of working on an ambitious project to build a 21...
  44. B

    Relationship between interference and arm length in MZI

    A question about the Mach-Zehnder interferometer. My understanding is: If its two arms are equally long, there is destructive interference in one output and constructive interference in the other output. So, the intensity of light detected at the first output should be 0% and at the second...
  45. H

    B Why does a LIGO arm stretch and not move in unison?

    LIGO is most sensitive to a GW from directly above/below. As a transverse wave hits an arm why don't the laser source and the mirror move in unison -- thereby covering up the distorted motion?
  46. BillTre

    DNA Based, Charge Controlled, Nano-Scale Arm

    This Science magazine news article describes a nano-scale arm made of DNA whose postion is controlled by charge. There is a little movie too.
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