Exam 1

Question 1

What is an example of a common obstacle we
encounter in inverse kinematics problems

Answer 1

Inverse kinematics problems often have more than one solution, and the system of equations is nonlinear. When solving for a combination of acceptable angles, we often will find a combination that is physiologically
impossible/improbable.

Need to use Fsolve

Question 2

When solving an underdefined system of equations (common in biomechanics) using the
pseudo inverse in MATLAB, what additional assumption is used to select a combination of
forces from the infinite available possibilities?

Answer 2

Pinv() minimizes the solution vector. This aligns with the idea that we will select the most efficient combination of muscle forces..

Question 3

When dealing with multiple unknown muscle forces, it is possible to link them all back
to a single variable dependent on the relative muscle geometry. Briefly list the assumptions
associated with this approach

Answer 3

we assume that 10 muscles exert a unifrom maximum pressure and that 2) all muscles will engage the same percentage of their maximum force. This allows us to write theri ration of forces as a function of their ratio of cross-sectional areas.

Question 4

Provide an example of an activity where quasi-static equilibrium would likely
be a poor choice for estimating the forces involved

Answer 4

Running or anything where you are moving with speed/ the force you exert depends on the quickness of the motion you are performing

Question 5

What is the relationship between the pressure applied by the weight of an
object on ground and the resulting normal force? Where should the normal
force be applied ?

Answer 5

Normal force is equal to the integrated pressure in opposite direction under statics. It should align with the center of gravity of the object.

Question 6

mechanics

Answer 6

nehavior of physical bodies when subjected to mechanical disturbances such as forces or displacements and the subsequent effect of the bodies of their environment

Question 7

bio-mechanics

Answer 7

concerned with the application of classical mechanics to biology. It combines engineering mechanics wiht biophysics

Question 8

assumptions and fators for making a model

Answer 8

recognize its limits, simplify it, the more detailed the harder to solve.

Question 9

common limits for engineering models

Answer 9

small deformations, linear stress-strain behavior, negligible dynamic effects

Question 10

what do forces represent

Answer 10

load distributed over an area (pressure)

Question 11

coplanar system

Answer 11

forces acting on a 2d plane or surface

Question 12

colinear

Answer 12

if all forces have a common line of action

Question 13

magnitude of moment

Answer 13

Equal to the force times the shortest difference to the pt. M=Fxd

Question 14

external forces

Answer 14

forces applied to an object externally

Question 15

internal forces

Answer 15

forces that hold the body togetehr when the body is under the effect of externally supplied forces

Question 16

well defined

Answer 16

has as many equations as unknowns

Question 17

underdefined

Answer 17

has more unknowns than equations

Question 18

overdefined

Answer 18

has more eqautions than unknowns

Question 19

multiple muscle groups solving

Answer 19

1. assuming single muscle group activated
2. assuming the muscles are equally activated
3. optimization of expenditure

Question 20

optimization

Answer 20

we solve this by assuming the lowest energy necessary for completing the motion( high efficiency)
pinv() or isqnonneg()

Question 21

direct kinematics

Answer 21

calculate the end pt given all other measurments

Question 22

danvit harten berg matrix

Answer 22

vector based-approach to solve kinematics and range of motion

Question 23

inverse kinematics

Answer 23

calculates joint angles and positions given an end point, nonlinear, multiple solutions, fsolve

Question 24

Fsolve

Answer 24

needs sys of eqs paramaters and initial guesses