What are the muscles, joints and bones used when throwing a ball?
Bringing the ball back: The Posterior Deltoid causes the Glenohumoral Joint (shoulder) to horizontally adduct and externally rotate. The Anterior Deltoid stretches to slow the external rotation and the Pectoralis Major stretches to slow the horizontal adduction. Also, the Back Extensors and Obliques cause trunk rotation. In the lower body, the Rectus Femorus and Illiop Psoas flex the hip, bringing the leg up. Throwing the ball: The Pectoralis Major and Anterior Deltoid work in conjuction to both internally rotate and horizontally abduct, moving the ball forward. At the same time, the Triceps Brachii extends the elbow, providing more forward vectors. Also, the Abdominals and Obliques rotate the trunk toward the throw, also increasing forward vectors. On the lower body, the Quadriceps extend the Femorotibular joint (knee) and the Glutes extend the hip, which further increases the forward vectors. Recovery: The Posterior Deltoid must undergo massive stretching to slow the motion of the arm (the reason for common Anterior Shoulder Subluxations). The rear leg comes off the ground involuntarily to balance the throw and to bring the pitcher back to a normal position
What muscles are involved in hammering?
a. During gripping activities, “the muscles of the flexor mechanism in the hand and forearm create grip strength while the extensors of the forearm stabilize the wrist”. There are four major joints of the hand, Carpometacarpal, Intermetacarpal, Metacarpophalangeal, and interphalangeal joint, with “9 extrinsic muscles that cross the wrist and 10 intrinsic muscles with both of their attachments distal to the wrist.” These muscles include the pronator radii teres, flexor carpi radialis, flexor carpi ulanris, flexor sublimis digitorum, and Palmaris longus on the extrinsic layer and the flexor profundus digitorum, flexor policus longus, pronator quadratus, flexor pollicus brevis, and abductor pollicus brevis on the intrinsic layer. Each of these muscles is active during gripping activities! b. Flexor pollicis longus, lexor digitorum superficialis, flexor digitorum profundus, lumbricoides, adductor pollicis c. Flexor digitorum superficialis, flexor carpi ulnaris, flexor capri radialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, extensors pollicis longus and brevis. d. Abductor pollicis longus, abductor pollicis brevis, extensor digitorum, e. Triceps (extension) and biceps, brachilais (contraction)
What are the mechanisms used in steering system and describe them?
If I may, would like to show the comparison between the two main types of steering linkage on most passenger cars, which has been overlooked in the other answers. The older worm-and-sector or worm-and-roller required more moving links and articulated joints. One advantage was that it tended to isolate the driver from road wheel impacts telegraphed through to the steering wheel. Conversely this resulted in less "road feel" that would alert the driver of tire grip (or lack of) on the road, and more pivot joints leading to poorer mechanical precision.When power assisted steering was first offered, it was accomplished by attaching an hydraulic piston/cylinder to the central tie rod, which helped to dampen shocks felt at the steering wheel, however, this made for an extra component - not counting the hydraulic, oil reservoir, drive belt, hoses valves. etc. By substituting with the rack and pinion system, which was originally unassisted, the hydraulic cylinder and valving were integrated with the rack housing, and resulted in a simpler, more precise steering linkage.A recent modification to the rack type has been to reduce the gear tooth spacing at the center of travel, so that the steering ratio, i.e., the relation between the degrees turned at the steering and the degrees of hub movement will be less sensitive in straight-line travel, but increase when steering through a curve. It should be noted that since the steering pivot arms on the wheel hubs rotate. the "steering ratio" will effectively increase (degrees of steering input/degrees of hub pivot travel) as they swing towards their limit, so all steerings are sort of variable ratio.
Why are stepper motors used for robot joints instead of other motors?
To understand my answer well you need to get the difference between a stepper motor and an ordinary dc/ac motor.Let me give an example ,consider the motor of your fan(an ordinary motor),the only control you have over it is of turning it on or off and changing its speed. Now say you want to rotate the motor through one and a half revolution only, how do you do that?Now take your printer(which uses a stepper motor). You want to take in the paper and take it out, now that requires a specific number of revolutions. What your stepper motor does is that it completes one revolution in steps. These steps can be from 2–10000(i.e. One revolution could be completed in 2 or 10000 steps).Incase of joints in robots,cnc machines,etc you need accurate movements which calls for precision in the movement of motors hence stepper motor are used. They also make use of servo motors.
Wrist Pronation on Forehand?
k, i think that there's a certain wristiness with every grip. I used to play with a western, but now changed to semi, due to arm injuries, and i know what you are talking about. For pronation with a western u can see it especially clear with a nadal video, (links on bottom) either with his windshied-wiper motion or over the head motion, theres a split second during hitting and a bit after contact that he turns his wrist. It's hard to see in the novak video, bad angle too. but it's slight, because he's using an over the shoulder finish, which in turn makes the swing look more semi-ish, and hides his racket hand after the follow-through. So we cant really see how much his wrist turned. Basically, a semi or western, hit properly with the user pulling back properly and then accelerating the racket forward with the butt-cap pointed towards the ball, and making contact with the ball correctly, will have a certain amount of wrist pronation, (but very brief, u probably wont feel it, if you hit with enough racket head speed) if done naturally and relaxed. But with or without pronation, as long as you can hit from take back to follow-through properly, should give you a pretty decent forhand. Look closely at the nadal's vids, and at his wrist. thanks. http://www.youtube.com/watch?v=yEjtLGMd2p8&feature=related http://www.youtube.com/watch?v=kNyfckDtRHM&feature=related
Is there a common standard for field operations hand signals used by police and military?
As with so many things in law enforcement, the answer is "yes and no." You need to first understand that there are about 18,000 law enforcement agencies in the U.S., and no two of them do things in exactly the same way. Some agencies have no formally adopted and taught hand signals at all, while others make extensive use of them. Of the agencies that do use hand signals, most are based on military/infantry signals. A raised fist means "hold" (stop), circling an upraised finger in the air means "gather around me," and a forward wave means "move forward." Most cops would understand these, if only because they had seen them on TV or in the movies. Here's the signal for "gather around me" or "rally;"There is a more complete list here: Hand Signals. A friend of mine, Bob Dent, joined forces with a retired Navy SEAL commander and taught a program of "Silent Universal Signals for Law Enforcement" in the 1990s, but it didn't catch on nationally. There's an article about it here: Spokesman Article on Redmond Training. I thought the system would be very useful in the field, but of course it's not much good if everyone doesn't understand the signals. Tactical (SWAT) teams are probably the most likely units to train with hand signals. Tactical team members are more likely to remember and use the signals frequently, as they train in practical tactics more often than cops who aren't tactical team members. As with radio codes and jargon, a cop from one agency might not have any understanding at all of signals and codes used in another. There is very little standardization here. For example, the radio code "10-10" means "residence" in most California agencies ("I'll be out at my 10-10 for lunch"), but in other parts of the country, it means "fight" ("Send cover for a 10-10 at 2nd and Main."). As for unusual hand signals, most of these would be signals intended to be humorous. Guns and Ammo magazine has an article about those here: The Real Meaning Behind Police Hand Signals - Guns & Ammo. There have been similar lists of fictitious/humorous radio codes, such as the "12-code." I remember a couple of those were "Send a K9 to help the fire department find a hydrant" and "I didn't understand you. Are you sitting on your microphone?"
What are the causes that I woke up with my thumb joint feeling painful?
RMI. Repetitive Motion Injury. Everyone gets these types of injuries repeatedly throughout their lives because most people don’t even think about proper care of their muscles. “Arthritis ,” is the term often used to describe pain problems the doctors don’t have an answer for, but that word is misused and abused.In a car, if the pistons are running hot with no lubrication, what happens? Even belts in the car…if they don’t have proper lubrication, what will happen? If there is no oil, or transmission fluid for a long period of time, is the car going to continue to run at optimal levels? No. It won’t. It is the same with us.Lubrication comes to muscles and joints via water…lots of it. If you aren’t drinking enough, if you are dehydrated, then obviously, problems will result. Nutrients come via the blood. If you overuse any part that of your body and don’t stretch regularly, then you will be overcontracted and pain will result. If you are overcontracted your blood pressure will be higher, and your body still won’t get the nutrients, plus your heart will get strained. It’s like damming up a river.By stretching regularly, I’m referring to yoga for an hour per day if you are not lifting weights. If you are lifting weights, your ratio of overcontraction triples, therefore, you need 2–3 hours of stretching for every 1 hour of weightlifting you do.It sounds like your hand, particularly your thumb is overcontracted and has been for a while. You need to stretch your hand and perhaps find a massage therapist in your area that knows how to release the muscles of the hand.
What is the function of the humerus bone in the human arm?
The humerus is an essential bone involved in all arm motion and central to the leverage and strength applied by the forearm, by the nature of it connecting the elbow and the shoulder. However the humerus is also one of the most accident sand fracture or dislocation prone bone and joint part of the human skeleton and as such has become a major focus for surgeons and therapists because the upper joint connects to the shoulder can be dislocated and fractured very commonly. I think the humerus is used most often as a support for the upper body and as part of the lift when standing from an awkward position. In the martial arts and combat sciences, the humerus needs to be conditioned in two distinct ways.First to take a strike from a kick or fist, so you learn how to hold and close ground against an aggressive fighter and to have dynamic forward compression to keep the elbow dynamic so the arm will not get pinned in a clinch or react in such a way that the center of momentum is manipulated at an inopportune time.
Why are the thumb movements defined differently to that of the fingers in the body?
All of the motions that you’re referring to are considered axial motions. Meaning, at each joint, there are 1–2 invisible axes at which motion occurs. These invisible axes that I’m referring to determine the direction of motion (and the plane at which the motions are occurring).If you were to take a kinesiology class, one of the first things that you would learn is that all motion starts from anatomical position.What you’re seeing in the image above: The thumb is in a position of flexion at a joint that is closer to the wrist than the other two joints that allow for motion of your 1st digit (i.e., flexion of the thumb at the 1st carpometacarpal joint.) Motion back to anatomical position is referred to as extension.Flexion of digits 2–5 would include forward motion of all four of those fingers. Of course, extension is how you would describe motion back to anatomical position.The reason that the path of motion for flexion of the thumb appears to be different from the other four fingers is that the invisible axis is oriented in such a way that it’s closer to being perpendicular to a different plane.Said another way, flexion and extension primarily occur in what is referred to as the sagittal plane. The one exception to this is that flexion and extension of the thumb occurs in the coronal plane.Now, to be clear, if you were to flex your thumb at the two joints that are farther from the wrist, then, those motions would be occurring in the same plane as fingers 2–5. This is due to the fact that the axes that are located at the two joints that are farther from the wrist are going in the same direction as the axes in digits 2–5.The bottom line: The invisible axes at a joint determines the plane at which motion will occur.
What are some different methods of controlling a robotic arm?
In depends on the robotic arm.For a pre-built robotic arm such as that of the KUKA robot, they can be controlled via directly programming the robot. This is because they have pre-built programs and electrical circuits systems allowing for them to handle all of the low level control and allowing you to only examine the high-level aspect of it.If you are talking about having a series of servos/motors/other mechanism of motion linear/rotation/etc. put in series to develop an “arm.” (Here my answer will only apply to motor control) These are controlled via electrical signals implementing in general voltage or current control. Voltage, in general, corresponds directly to the speed at which the motors will move. Current, in general, correspond directly to the torque at which the motors will move. This is by implementing the motor constant (which isn’t truly constant but is often modeled as).Often robot arms are desired to follow some trajectory of motion. As such, encoders or some other mechanism of detecting the position of the arm in space is used and this is correlated with desired position and a PID (proportional, integral, derivative) controller can be used to track the position with forward kinematics. Impedance controlIf you are really interested in learning more about this I would recommend to look up information on:control systems (pid, adaptive control, state-space control, etc.)how electric motors work (stepper, brushless dc, brushed dc, ac, etc.)forward/inverse kinematicsPlease let me know if anything here is unclear and I will do my best to clear it up. This isn’t an entirely in-depth answer.