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MED 101- PHYSICS I > 6. KINEMATICS (STANDING, RUNNING AND WALKING) > Flashcards

6. KINEMATICS (STANDING, RUNNING AND WALKING) Flashcards

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1
Q
  1. What is Kinematics?
A
  • it is a branch of mechanics
  • it deals with the motion of bodies
  • it does not consider mass or force
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2
Q
  1. What does Kinematics involve?
A
  • it involves tracking the motion of the centre of mass of the body
  • it involves tracking the angle vs the time
    -it involves tracking the angle versus the angle
  • this is all tracked during the walking or running cycle
  • the three angles that are tracked are:
    • the angle of the thigh
    • the angle of the knee
    • the angle of the ankle
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3
Q
  1. What are the angles changed by?
A
  • they are changed by the forces
  • these forces are controlled by different muscles
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4
Q
  1. What is the criteria for overall stability during standing?
A
  • the centre of mass has to be over the area spanned by the feet
  • the vertical line passing through the centre of mass has to pass through the area of the support base
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5
Q
  1. What do stable joints indicate?
A
  • local stability
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6
Q
  1. What is the formula for working out pressure?
A
  • P= F/A
  • Pressure = force divided by area spanned
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7
Q
  1. What is the SI unit for pressure?
A
  • Pascals (Pa)
  • this is known as a Newton per square metre (N/m2)
    (kg.m⎺¹.s⎺²)
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8
Q
  1. How would you work out the pressure on the feet of a 71kg person?
A
  1. 71kg x 9.81 = 700N
  2. 700N / 2 = 350N per foot
  3. Total cross-sectional area of the two feet= 350cm²
  4. 350cm² / 100² = 0.035m²
  5. Pressure = F / A
    = 700 / 0.035
    = 20 000 Pa
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9
Q
  1. What is the relationship between Pressure and area?
A
  • they are inversely proportional
  • pressure is decreased when the area increases
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10
Q
  1. Does your whole foot touch the ground when you are standing?
A
  • no
  • most of the contact is at the ball and the heel of each foot
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11
Q
  1. What is higher on the ball and the heel of each foot?
A
  • the pressure
  • it is almost 5x higher
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12
Q
  1. What is higher on the feet and why?
A
  • the peak forces (pressure) are higher on the feet during walking
  • this is because only one foot is on the ground at a time
  • this means that there is a smaller area being spanned
  • this results in a higher pressure
    (pressure on the feet that is exactly 2x higher than
    the pressure on the feet during standing)
  • the force on the foot is twice that than with both feet on the ground
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13
Q
  1. What are the normal forces involved in with regards to walking?
A
  • braking
  • forward repulsion
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14
Q
  1. What changes with the magnitude of the normal forces during walking?
A
  • they are two times greater than the magnitude of the normal forces during standing
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15
Q
  1. What makes the contact area between the ground and the foot much less during walking?
    What does this result in?
A
  • the whole foot is not flat on the ground during most phases of walking
  • this increases the peak-pressure during walking to be 30 times higher than during standing
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16
Q
  1. How are routinely force plots measured?
A
  • they are measured during motion
  • they make use of pressure sensors
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17
Q
  1. What are the multiple bones in the human foot suspended by?
A
  • they are suspended by a series of muscles and ligaments
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18
Q
  1. What does the suspension of the muscles and the ligaments form?
    What is the function of this?
A
  • it forms the foot arch
  • this arch assists in stability during standing
  • it helps with walking
  • it allows movement to be a low energy consuming activity
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19
Q
  1. What happens when the foot hits the ground?
A

-the arch flattens

  • as the arch restores:
    - the foot is propelled forward by the toes
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20
Q
  1. What are the disadvantages of bipedal movement?
    (spreading the weight on two feet instead of four?
A
  • tendency to cause lower back pain
  • sprained ankles
  • knee problems
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21
Q
  1. What is the similarity between the kinematics, forces and energetics of walking and running?
A
  • in both walking and running:
    - the foot pushes back to get a forward reaction force
    - the normal force is always acting upwards on the foot
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22
Q
  1. Why is it harder to walk in sand?
A
  • there is a small reaction force on the feet until the sand is compressed
    (this is indicated by your footprints)
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23
Q
  1. How do your footprints in the sand look?
A
  • they are deeper in the front than at the heel
  • this is because the foot is pushing off (backwards) in the sand
  • there is a stronger force
  • this produces more pressure
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24
Q
  1. What are the 7 stages of walking?
A
  1. Heel Strike (initial contact)
  2. Loading Response (foot is flat)
  3. Mid Stance
  4. Terminal stance (heel is off)
  5. Pre swing (toe is off)
  6. Initial and Mid-swing
  7. Terminal swing
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25
Q
  1. What are the two time periods that the hip, knee and ankle angles are usually related to?
A
  1. When the foot touches the ground (FS)
    - this is known as the Foot Strike
    - it is also known as the heel strike/contact
  2. When the toes leave the ground (TO)
    - this is also known as the toe off
    - it is also known as the foot off
26
Q
  1. What is the stance phase?
A
  • this is the phase found between the foot strike
    (when the foot touches the ground)

AND the toe off
(when the toes leave the ground)

27
Q
  1. What is the swing phase?
A
  • this is the phase found between the toe off
    (when the toe leaves the ground)

AND the foot strike
(when the foot touches the ground)

28
Q
  1. When does the stance phase occur for walking?
A
  • during the first 60%-65% of the cycle (Gait Cycle)
29
Q
  1. When does the swing phase occur for walking?
A
  • during the last 35%-40% of the cycle
30
Q
  1. When are there two feet in the ground during the gait cycle for walking?
A
  • during the first 10%
    (just after the foot strike)
  • during the last 10%
    (just before the toe off)

OF THE STANCE PHASE

31
Q
  1. Are both feet ever on the ground at the same time?
A
  • NEVER
32
Q
  1. What is the Kinetic energy of the body dependent on?
A
  • it depends on the objects mass
  • it depends on the speed of its centre of mass
33
Q
  1. What can the total Kinetic Energy be split up into?
A
  • it can be split into:
  • the kinetic energy due to motion in the horizontal plane
    (the x axis)
  • the kinetic motion due to motion in the vertical plane
    (the y axis)
34
Q
  1. What is the formula for the total Kinetic Energy?
A

KE= KE horizontal + KE vertical

 = (½ x m x v²) horizontal + (½ x m x v²) vertical

NB: your focus is on the initial velocity

35
Q
  1. What is the formula for the potential energy?
A

PE = mgh
= mass of the body x gravity x the length on the y axis

36
Q
  1. How do we describe a system where the energy is not supplied or lost?
A
  • we describe the total energy of the system as constant
  • this energy does not increase or decrease
  • this is because the total energy of the system is conserved
37
Q
  1. What is the formula for the total constant energy?
A
  • E = KE + PE
38
Q
  1. Is the total energy completely constant during walking?
A
  • no
  • it is almost constant
39
Q
  1. How long is each foot on the ground for during running?
A
  • it is on the ground for less than half the time
  • sometimes neither foot is on the ground
40
Q
  1. Describe the running process?
A
  • the runner starts in a four-point stance
  • they then push off of the starting block with both legs
  • this gives them forward acceleration
  • the body is fairly horizontal at first
    (this is to keep pushing the runner forward)
  • the runner than accelerates as fast as possible
  • the body becomes vertical to increase the stride length
  • this helps to reach and maintain maximum speed over the finish line
41
Q
  1. What is one difference between walking and running?
A
  • the leg becomes almost straight during walking
  • it never does this during running
42
Q
  1. Which % is higher during running, the stance or the swing?
A
  • the swing % is greater during running
43
Q
  1. When and in what quantity does the stance occur?
A
  • the stance occurs during the first 40% of the gait cycle
  • this is after the foot strike
44
Q
  1. When and in what quantity does the swing occur?
A
  • it occurs during the next 60% of the gait cycle
  • this when the foot is off the ground
  • this is from the toe off to the next foot strike
45
Q
  1. Which other limbs move during running?
A
  • your arms swing back and forth
  • your torso rotates
  • both are 180° out of phase with your legs
46
Q
  1. What does the height of your jump depend on?
A
  • how fast you can take off
47
Q
  1. What are the 4 stages of a vertical jump?
A
  1. standing
  2. crouch
  3. take-off
  4. free-flight
48
Q
  1. What happens to the centre of mass when the person crouches?
A
  • it decreases
49
Q
  1. What happens to the centre of mass when the person takes off?
A
  • it increases
50
Q
  1. What is the speed of the person at the top of the Free Flight phase?
A
  • it is 0m.s⎺¹
51
Q
  1. When does the extension phase start and end?
A
  • it starts after the crouch
  • it ends before the take-off
52
Q
  1. What happens to the centre of mass and the velocity of the person during the extension phase?
A
  • the centre of mass rises by the distance between the centre of mass and the hip joint
  • the velocity equates to the velocity of the take off from the ground
53
Q
  1. What happens to all the kinetic energy at takeoff?
A
  • it is converted to potential energy at the top of free flight
  • this means that the mechanical energy is conserved
  • this means that we need to use the mechanical energy formula when doing equations on this topic
    (ME= KE + PE)
54
Q
  1. What formula can you use to work out the vertical height achieved by the person that is jumping?
    (when velocity is given)
A

H = v² (of the take off)
_______________
2g(9.81)

55
Q
  1. What formula can you use to work out the vertical height achieved by the person that is jumping?
    (when time and distance is given)
A

H = 2 x (distance) ²
_______________
g x (time) ²

56
Q
  1. What is the mathematical relationship between extension time and the height of the jump?
A
  • the height of the jump is greater when the time is decreased
  • the two are inversely proportional
57
Q
  1. What do both legs generate during extension?
A
  • they both generate a normal force
  • these two FN forces together make up the net force
    (total vertical force)
58
Q
  1. Read Summary one.
    Does everything make sense?
A
  • yes
59
Q
  1. Read Summary one.
    Does everything make sense?
A
  • yes
60
Q
  1. Read Summary three.
    Does everything make sense?
A
  • yes
61
Q
  1. Read summary four.
    Does everything make sense?
A
  • yes
62
Q
  1. Read summary five.
    Does everything make sense?
A
  • yes

MED 101- PHYSICS I (28 decks)

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