Question
A person holds an object of mass m = 4.2 kg on the palm of the hand with the arm stretched. Use the torque equilibrium equation to determine the magnitude of the force F exerted by the biceps muscle when a = 25 cm, b = (0.15 · a), and the angle θ = 75°. Neglect the weight of the lower arm
Answers
Anna
(a+b)(Fg)-b(Fcosθ) = 0
-->solve for F
Have you done #1 or #3 of the assignment? If you have, please help!
-->solve for F
Have you done #1 or #3 of the assignment? If you have, please help!
Mia
No but I am going crazy trying to do the calculations! Grr...wish I had more time to review before doing this h/w!
Thanks though. If I figure it out i'll post back here, ok
Thanks though. If I figure it out i'll post back here, ok
Karina
Hey Anna, can you break that down. I'm so confused!
Mia
Fg in the eqn she gave is mg...
Mia
Did any of you guys find 1 or 3?
Anna
So, basically i wrote down the torque equilibrium equation where torque equals 0 and the point of reference being the one shown in the diagram. The distance from the point of reference to where Fg is applied is a PLUS b since a is just the distance from the point where F is applied...NOT from the point of reference. The signs you can find using the right-hand rule..i used positive as counterclockwise..so torque is pointing towards you.
Mia
Anna if u are having trouble with number 3, have a look at Ex5.2 it will help.
Karina
these are the steps to do number 3. i still have yet to try it though:
first you need all the euations of the forces
so horizontal and vertcal
then you need torque
so once you hv your torque youll hv lots of L
you should factor that out
nd solve for T
then sub T into the horizontal forcees equation
nd solve for Rx
And for Question 2 are we supposed to convert cm to m and when we find b, there's no given units so am i supposed to just multiply it with a and it automatically becomes the same unit as a?
first you need all the euations of the forces
so horizontal and vertcal
then you need torque
so once you hv your torque youll hv lots of L
you should factor that out
nd solve for T
then sub T into the horizontal forcees equation
nd solve for Rx
And for Question 2 are we supposed to convert cm to m and when we find b, there's no given units so am i supposed to just multiply it with a and it automatically becomes the same unit as a?
Anna
the units are given.. it's cm throughout..you don't have to convert because the units for l get canceled out in the end anyways
i got an answer around 3000 for #3? Anyone else get something similar?
i got an answer around 3000 for #3? Anyone else get something similar?
Karina
yep, it's supposed to be a huge number for #3
Karina
i got around 4000s. Hey for question 2 is it supposed to be a tremendous number as well. I got like 4450
Ann
Did anyone figured out #1?
Anna
No! I've tried multiple ways to do it.. and yet still not getting the right answer. I think I'm messing up my coordiante system and the angles for the forces..
Karina
Question #1
T(l1)cos30 + Warm(l2)cos30 - WM(l3)cos30
solve for T
T(l1)cos30 + Warm(l2)cos30 - WM(l3)cos30
solve for T
Anna
time's up..lol
Thanks guys!
Thanks guys!