week 3

Question 1

standing analysis starts with a discussion of

Answer 1

overall stability, local stability, and friction

Question 2

kinematics

Answer 2

the branch of mechanics dealing with the motion of bodies, without considering mass or force

Question 3

what does kinematics involve?

Answer 3

1. tracking motion of the center of mass of the body
2. tracking angles vs time and vs each other during a walking or running cycle (θknee,θthigh, θankle)

Question 4

what is essential during standing, and any other type of motion?

Answer 4

stability

Question 5

what is the criterion for overall stability during standing

Answer 5

• for the center of mass to be over the area spanned by the feet
• this means that a vertical line passing through the center of mass passes in this area of the support base

Question 6

how does overall stability indicate local stability?

Answer 6

• overall stability presumes a rigid body and consequently rigid joints
• such stable joints indicate local stability

ex: a human knee

Question 7

how is the pressure on the foot during walking twice than that during standing?

Answer 7

• the peak-forces on the feet are much higher during walking
• since during walking only one foot is usually on the ground
• this means that the force on that foot is twice that with both feet on the ground (during standing)
• so, the pressure is twice than during standing

Question 8

what is the foot arch used for?

Answer 8

to assist stability during standing and helps walking

Question 9

what are the disadvantages of spreading our weight on 2 feet rather than 4?

Answer 9

1. tendency to lower back pain
2. sprained ankles
3. knee problems

Question 10

what is one similarity between walking and running?

Answer 10

the foot pushes back to get a forward reaction force

Question 11

during the stages of walking, the hip, knee, and ankle angles are usually referenced to the time ____?

Answer 11

1. the foot touches the ground, foot strike (FS) or heel strike/contact
2. when the toe leaves the ground (toe off, TO)

Question 12

from foot strike to toe off we have the?

Answer 12

stance phase

Question 13

from toe off to foot strike we have the?

Answer 13

swing phase

Question 13

for walking, the stance phase occurs during the first _____ of the cycle and the swing phase occurs during the last _____ of the cycle

Answer 13

• 60-65%
• 35-40%

Question 13

when we describe a system where energy is not supplied or lost, the total energy E of this system is constant, where:

Answer 13

E = kinetic energy + potential energy

Question 13

what does the KE of an object depend on?

Answer 13

the object’s mass (mb) and the speed of its center of mass (u)