how much force must you exert to keep the pole motionless in a horizontal position? This is a topic that many people are looking for. bluevelvetrestaurant.com is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, bluevelvetrestaurant.com would like to introduce to you Physics – Mechanics: Ch 15 Torque (13 of 27) Body Mechanics: Ex. 1, F=? To Lift Up Arm. Following along are instructions in the video below:
To electron line. It turns out that mechanics and torques are very prevalent in the the study of human mechanics body mechanics for example how much tension does the tricep to apply in order to take your arm and lift it up into a horizontal position your muscles. I can do that is the muscle thats attached to your your skeleton right here in your arm.
It would be the tricep thats connected to the humerus in the upper arm and thats the muscle that can pull your arm up into a horizontal position how strong is that muscle how strong that muscle need to be in order to accomplish that well heres the physics of it all lets say that the weight of the arm. When its stretched out like that is 50 newtons and the center. Mass is about 30 centimeters away from the joint in the shoulder.
The tricep is connected to the bone. About 8 centimeters away from where the arm pivots right here in the shoulder joint the angle of that that muscle makes is about 12 degrees relative to the horizontal when the arm is outstretched like that lets find out what force is required on that from that muscle in order to get your arm b. And hold it in that particular position again.
We can say that the sum of all the torques about the pivot point. Lets call. The paper part right here.
Lets call that pivot point a about pivot point. A must add up to zero first of all we have the weight of the arm relative to this pivot point. It gives that a clockwise direction of the negative torque.
So it would be equal to minus the weight times.
The perpendicular distance from the line of action of the force to the pivot point. Which would be 30 centimeters and we can leave it in centimeters because i believe centimeters will end up cancelling out so lets write it as 30 centimeters now we have the force caused by the tricep. Which is pulling the arm in a counterclockwise direction.
Thats a positive force or a positive torque. I should say that would be the force from the tricep now we have to multiply that times. The perpendicular distance from the line of action of the force to the pivot point as the distance right.
Here. Lets call that distance d. Now we need to figure out what that distance d is let me redraw that so you can easily what it looks like so heres the triangular shape that were talking about this distance.
Here thats a hypotenuse that is 8 centimeters. This is the distance. Were trying to find and this is the angle.
Which is opposite to the distance d. We can then see that d is equal to the hypotenuse of 8 centimeters times. The sine of theta.
Which in this case is 12 degrees.
And that would then go in here lets now plug that into our equation right here. We get. 0.
Is equal to minus mg that would be 15 newtons times 30 centimeters plus. The unknown force times d. Which is 8 centimeters times.
The sine of 12 degrees. Solving for f. Moving this to the other side and turning the equation around we have f times.
8 centimeters times. The sine of 12 degrees is equal to a positive. 15.
Newtons times 30 centimeters finally dividing both sides by 8 centimeters then science. All the greens. We have the force and that would be the force of the tricep is equal to 50.
Newtons times 30.
Centimeters divided by 8 centimeters and divided by the sine of 12 degrees. Lets find out of stronger tricep has to be we have 50 times. 30.
Divided by 8 and divided by the sine of 12 and we get 902 newtons 902 newtons. Thats a lot of force now lets convert that to pounds some of you will understand it better if we do this in pounds. We need pounds in the numerator and newtons in denominator.
One pound is equivalent to four point four four eight newtons. I believe thats correct. Ill have to look it up its close anyway.
Gives us alligators close enough so divided by four point. Four four eight equals and that would be 202 pounds. So 203 pounds.
So your tricep has to apply a force of about 200 pounds in order to lift up your arm. Here and keep it in that position. Thats quite something the skeletal structure and the way the human body works in the way the muscles move the body is actually amazing when you think about it theres only certain ways in which that can be done and it always requires very short distances from where the muscles are attached to where the pivot point is relative to where the center of mass of the weights are that youre trying to lift.
Therefore the muscles of the body youre actually extremely strong even though you may be lifting just very small weights like the weight of your arm. Which is very much it does require an enormous amount of force and the muscles. Its quite surprising how strong the human body muscles.
Actually are 200 pounds for a little tricep thats quite something and thats how its done you .
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