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. K

    Period of a Pendulum on an Arm

    Homework Statement The “Giant Swing” at a county fair consists of a vertical central shaft with a number of horizontal arms attached at its upper end. Each arm supports a seat suspended from a cable 6.17 m long, the upper end of the cable being fastened to the arm at a point 3.77 m from the...
  2. S

    Initial and terminal arm in trig

    For some of the questions questions the initial arm is in the positive x and y quadrent and the terminal arm moves counter clockwise (+)this is considered positive , for some of them it is in the negative x and positive y quadrent, how does one determine where the initial arm is to be placed...
  3. Y

    Angular velocity and acceleration for catapult arm

    Homework Statement This isn't a homework problem, but I'm trying to do the calculations for a catapult I built to see if its actual performance matches the theoretical performance. I'm stuck trying to map the trajectory of the projectile. Here is the picture for reference...
  4. M

    3d modeling of a suspension arm

    Hello, I am trying to model a basic automobile suspension arm in 3 dimensions. The model consists of basically a triangle made up of 3 vectors a, b, and c. Vector a is "ground" and magnitude and direction is known. Magnitudes of vectors b and c are also known. So, I can write the following...
  5. Z

    What is the length of the moment arm.

    So here's the problem: Bodybuilder “Hulk” Heise is doing leg curls on a Cybex machine. “Hulk” gets stuck (see figure) with 90° angle at the knee joint. The force exerted by the machines (FA) on his leg is 500 N, directed at an angle of 55° (angle α) relative to the tibia, and the distance...
  6. J

    Robot Arm Design: Calculating Torque Needed

    I am design a three jointed robotic arm that can lift 40 pounds. A diagram of the arm is attached. How can I calculate the torque needed at each motor to lift the 40 pounds?
  7. S

    How do I calculate the moment of load on an arm?

    Homework Statement Homework Equations So moment and torque are really the same, right? so the force times the distance. The Attempt at a Solution The force used has to be perpendicular to the line of the radius about O, so I assume I must do cos(36)*6lb*5in for the first. The...
  8. H

    Prosthetic arm amplifier and filter design

    Hello... Am undergraduate EE, and am working on my final year project which is the development of prosthetic arm which will work on signal from muscles taken from surface myoelectric sensors. First of all i will explain about circuits i want to build, and i wish i will have comments...
  9. V

    Forces acting on a Bowler's Arm

    Homework Statement Homework Equations T=rF The Attempt at a Solution I'm not sure at all how to solve this problem. If anyone can help me out with setting this up and proceeding from there that would be a big help.
  10. H

    Medical Exploring Nerve Signals for Natural Arm Movement

    Hello.. Am an Electrical Engineer, my FYP concerns the artificial limbs... I made a small research about the nervous messages, and how it flows from the brain until it reaches the muscles. In the arm i found that there are 3 nerves (Ulnar, Median, and Radial nerve) which are responsible for arm...
  11. M

    [NEED SOME TIPS] Robot Arm Designing

    hi everyone, I'm a mechatronics student. I'm sorry i posted this question here. I hope i can get some tips/answers/designs(rough design) http://i101.photobucket.com/albums/m62/minmonster57/Robot_Arm_Design.png I'm having this Robot building project. And faced a designing problem, This...
  12. T

    What is the Angular Velocity of an Arm at 45 Degrees?

    Homework Statement Compute the angular velocity (ω) when the arm reaches 45 degrees equation = ω^2 = ωi^2 + 2α(Δθ) α = 196.85 Homework Equations equation = ω^2 = ωi^2 + 2α(Δθ) The Attempt at a Solution 2(196.85)(45) ?? what do i use for ωi^2? or is it just 0
  13. P

    I have to find the speed that the end of the arm goes. Can anyone

    I have to find the speed that the end of the arm goes. Can anyone help i attached a diagram
  14. B

    Compensating Robot Arm Deflection for End Weight

    Hi guys, I'm doing a robotics project that requires me to compensate for the bending of the arm due to an end weight. I can calculate the deflection at the end of the arm for a given weight e.g. End link horizontal (90 degrees), end weight = 1000g, deflection = 10mm From this i can calculate...
  15. D

    What is the lenght of the lever arm? (when torque and force are given)

    Homework Statement If a torque of 55N.m is required and the largest force that can be exerted by you is 135N, what is the length of the lever arm that must be used? Homework Equations Lever Arm=(r)(sin) Torque=(Force)(r)(sin) The Attempt at a Solution To be honest, I'm stumped
  16. L

    Floating Arm Trebuchet Calculations and Predictions

    So, like quite a few others on this forum, I am building a trebuchet for a school physics class. While I am really enthusiastic about the project (who doesn't love giant medieval war machines?), I may be a little bit over my head in the calculations. So I hope I can give enough information...
  17. T

    Build a $100 Robotic Arm with CCD Motion Capture

    http://builders.reprap.org/2009/09/bambot-bamboo-robot.html I want to see this design move forward. Before I can work on the mechanical engineering aspects of the motors: I want to work on my position control system. (Cheap geared DC motors like those from solarbotics/chinese drill motors...
  18. L

    Rotational inertia of arm lifting a cup

    Homework Statement Doc Holliday takes his last shot of whiskey. His forearm and hand spans 18" and weighs 2lbs. The shotglass and its intoxicating contents weighs 5ozs. (there are 16 ozs in one pound). Doc remains otherwise motionless as his elbow bends, tossing back the whiskey. Calculate...
  19. E

    Torque Of Lever Arm in 1st/2nd Class Levers

    Part 1 - Question About Torque Of Lever Arm in a 1st Class Lever Homework Statement A little while back I posted a question about incorporating the torque of a uniform mass and dimension lever arm into the principle of a 1st class lever. Here is the thread for reference...
  20. W

    Extending arm with counterweight balance question

    Hi guys, I'm working on a prototype for a lamp and have quickly overreached my meagre school boy mechanics skills, almost at the first hurdle, in fact. Embarrassing, I know, but hopefully some kind soul here will be able to point me in the right direction. A picture is worth a thousand words...
  21. M

    How to Optimize Steering Arm Angle for Rear Steer and Ackermann in FSAE Design?

    Hi :smile:! I am doing the steering of our FSAE(formula racing car). will be using rear steer with a lot of ackermann. One particular strategy i came across for finalising stering arm angle is, you vary your steering arm angle (angle seen in plan between steering arm and uprights) so that...
  22. D

    Finding the rotational moment of inertia of a multihinged arm

    Homework Statement I'm trying to calculate the moment of inertia of a multihinged arm, with one joint at the shoulder and a second joint at the elbow. Each joint has a set of local axis, with y being a vector pointing down the shaft of the cylinder, z being a vector pointing up, and x being...
  23. S

    How Much Torque is Needed to Lift a 0.44m Robot Arm?

    I'm having some trouble working out the required torque for a motor to lift a robot arm for my university project. My design is cable driven so all the power has to be transmitted thorugh cables with motors at the base. please could anyone help me work out how much torque is required to lift...
  24. H

    Calculating the torque in a moving arm of a catapult

    Find the ideal energy transferred to a projectile in a spring launching device, the device is a catapult which involves a bungee cord being stretched and has the cord attached to a throwarm which is pivoting on a circular rod. i have calculated the elastic energy stored in the cord at the...
  25. M

    Help Torque to drive robot arm

    Hi I am trying to designing a robot arm but am having problems calculating the torque required to drive the main shoulder joint. The arm is 700mm long and weighs 3Kg with a mass on the moving end of 6Kg. The arm is required to rotate repeatedly through 180deg then reverse back to the starting...
  26. T

    How Much Weight Can a Bodybuilder's Deltoid Muscle Hold Horizontally?

    Homework Statement A bodybuilder holds a dumbbell of weight Wd as shown in Figure 9.8a. His arm is extended horizontally and weighs Wa = 31.0 N. The deltoid muscle is assumed to be the only muscle acting and is attached to the arm as shown. The maximum force M that the deltoid muscle can...
  27. S

    Need help in build a cylindrical arm robotfinal project

    I am a student at ungku omar polytechnic.i want to ask someone that is good in engineering robot.i want to know how to make the cylindrical robot,do i have to used ball screw or belting as an actuator.I want to a build a small robot only about 550mm long and 650 mm hight.It can pull load of...
  28. U

    Floating Arm Catapult: Understand How It Works

    I saw a youtube video featuring a floating arm catupult, but I don't quite understand how it works. Could someone give an explanation to help me understand?
  29. C

    Universal joint/ball bearing controlled rotating arm for a furniture fitting

    Universal joint/ball bearing... controlled rotating arm for a furniture fitting Hello forum, I need your help on a furniture project we are developing in the office. its basically a floor standing lamp which needs to have a user regulated rotating arm. We are right now looking at different...
  30. wolram

    Can Being Odorless Lead to a Longer Life?

    I know the smell is produced by bacteria, but will an odour less person live longer than a smelly one? the bacteria must rob some of the life force from a body?
  31. W

    Torque with an arm holding a weight

    A man holds a 169 N ball in his hand, with the forearm horizontal (see the drawing). He can support the ball in this position because of the flexor muscle force M, which is applied perpendicular to the forearm. The forearm weighs 21.4 N and has a center of gravity as indicated. (a) Find...
  32. B

    Arm problem, Static Equilibrium

    Homework Statement (a) Calculate the magnitude of the force, FM, required of the "deltoid" muscle to hold up the outstretched arm shown in the figure. The total mass of the arm is 3.3 kg. (b) Calculate the magnitude of the force FJ exerted by the shoulder joint on the upper arm...
  33. M

    Calculating Moment Arm for a Force: Explained and Solved

    Homework Statement Homework Equations T=Fl The Attempt at a Solution I'm not sure what the moment arm of this problem is. I think it is suppose to be a line connecting 0 to F1 at a right angle. To draw this moment arm one would have to extend F1 past where it meets A. However I...
  34. D

    Help with robotic arm - fuel robot

    Hi, I have a college project running for which I have to design an automatic car refuelling cell. This includes automatic robot positioning, automatic payment, assisted car alignment et cetera. I like to stress that neither I nor my fellow students are mechanical or electrical engineers...
  35. J

    Calculating Torque of Athlete's Arm at the Gym

    Homework Statement An athlete at the gym holds a 2.2 kg steel ball in his hand. His arm is 74 cm long and has a mass of 4.0 kg. What is the magnitude of the torque about his shoulder if he holds his arm in each of the following ways? 1) Parallel out to his side 2) Straight but 35 M below...
  36. Evo

    Broken Arm Again - 3rd Time the Charm?

    Same arm, same place, fell in the backyard, same place as last time, third break. I didn't faint, although I came close. The Evo Child is on her way over, she wants to drag me to the ER, but I have a doctor's appointment in the morning anway.
  37. C

    [PhD Qualifier] Liquid in a rotating arm

    Homework Statement An open glass tube of uniform bore (uniform inner diameter) is bent into the shape of an "L". One arm is immersed into a liquid of density \rho and the other arm of length l remains in the air in a horizontal orientation. The tube is rotated with constant angular speed...
  38. ~christina~

    Medical Strange swelling on hands and arm

    I forgot about this for about 2 years. It all started, in the summer a few years back. My hand started swelling in a little patch on the top of my hand. I scratched it and it proceeded to swell up into a painful lump. (Is it always the case that swelling on the hands becomes painful due to the...
  39. M

    *Project* Building electrical (robotic) arm. Need help

    Hello, I'm an electrical engineering student and I've decided to build a robotic arm as a final project for one of my classes. Basically, my skills as far as building circuitry and solving electrical problems are at an intermediate level at this point, however, I'm not too familiar with the...
  40. Integral

    Moment of inertia of a hoop on an arm

    Homework Statement Find the moment of Inertial of a hoop at the end of a arm. The axis is at the end of the arm and normal to the plane of the hoop. Let: M= mass of the hoop r= radius of the hoop m=mass of the arm d=lengh of the arm Homework Equations I_{hoop} = Mr^2 I_{arm}...
  41. B

    What is the Torque on an Outstretched Arm with a 21.5 N Weight?

    Homework Statement A 21.5 N weight is held in the outstretched hand of a person with a shoulder-to-elbow length of 33.5 cm and an elbow-to-wrist length of 23.0 cm. The center of the weight is 6.5 cm from the person's wrist. Determine the magnitude of the torque about the elbow produced by the...
  42. C

    Calculating Required Torque with Support Arm

    Homework Statement Just looking for a general response - calculating required torque when there is a supoprt arm like in the attached doc. If there was no arm ... it's just F*d, but I guess the arm supports some of that force, so less torque is required? Homework Equations The...
  43. K

    Need help in designing cylindrical robot arm

    I'm currently designing the mechanism for a basic cylindrical robot arm. It must be capable of lifting max 2kg of item. The robot arm looks like ST Robotic R19 model. It moves in X and Z direction plus rotation at base and arm. The robot should looks like the attachment below. Can u please...
  44. S

    Newbie needed torque/moment arm design assistance

    Folks, hopefully someone can assist me. I am a EE by education and am in the process of designing a mechanism that I need some assistance on. The basic issue I face is determining the torque needed for a miniature drive motor/gearbox for this mechanism. The problem, I think, might be fairly...
  45. M

    If I swing my arm, it can emit gravitational waves?

    If I swing my arm, it can emit gravitational waves?? If I swing my arm, it can emit gravitational waves?? Thank you in advance!
  46. R

    How does gravity torque affect the position control system of a robot arm?

    I'm working on a developing a position control system for a robotic shoulder joint driven by a DC motor. To simplify, the robot arm can be viewed as being in a fully extended state. I have now reached a stage where I can no longer ignore the affect gravity has on the torque generated by the...
  47. P

    Arm length and angular motion in sports

    Last spring, I wrote on one of my blogs about an idea regarding the looping, underhand pitching motion in women's college softball. The idea is that tall, long-armed pitchers may derive greater velocity on their pitches than would shorter pitchers with shorter arms (overall body height and arm...
  48. S

    Torque on crane arm and load limit

    hello- i had this problem: the arm of a crane is 15.0 m long and makes an angle of 20.0 degrees with the horizontal. assume that the maximum load for the crane is limited by the amount of torque the load produces around the base of the arm. a) what is the mximum torque the crane can...
  49. K

    How Does the Deltoid Muscle Maintain Arm's Static Equilibrium?

    You are able to hold out your arm in an outstretched horizontal position because of the action of the deltoid muscle. Assume the humerus bone has a mass m=3.6, length L=0.66 and its center of mass is a distance L1=0.33 from the scapula. (For this problem ignore the rest of the arm.) The deltoid...
  50. S

    Ionized Arm Band: Does It Really Work?

    Recently I saw an infomercial for an ionized arm band thing which is supposed to improve your health. It seems like people think its works, and it supposedly has a patent on it, but how it works (if it does at all) was not explained in any detail. Does anyone know anything about this? I could...
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