Revision lectures

Question 1

What is kinematics

Answer 1

Kinematics deal with description of motion using scalars and vectors.

Question 2

What is kinetics

Answer 2

Kinetics is based on Newtons three laws of motion

Question 3

What is a scalar

Answer 3

Scalar is a measure of magnitude

Question 4

What is a vector

Answer 4

Vector is a measure of magnitude and direction

Question 5

What is differentiation

Answer 5

A derivative is the rate of change in a variable

Question 6

What is integration

Answer 6

Integration is area under a curve

Question 7

What is a projectile

Answer 7

An object in the air only affected by gravity and air resistance

Question 8

What are the three aerodynamic forces

Answer 8

Air resistance (drag), lift and magnus

Question 9

What variable allows you to determine if a person is walking or running?

Answer 9

Duty factor, under 0.5 is walking and over 0.5 is running

Question 10

How do you calculate duty factor?

Answer 10

Stance time divided by stride time

Question 11

What are the 5 phases of walking

Answer 11

Initial contact, loading response, mid-stance, terminal stance and pre-swing

Question 12

What are the 3 phases of running

Answer 12

Initial swing, mid swing and terminal swing

Question 13

What are the three differences between inertia and momentum

Answer 13

Momentum is the amount of motion a object has while inertia is the feature of an object that resists change in motion.

1. Inertia is direction specific
2. Inertia is specific to axis
3. You can change inertia during movement

Question 14

How is it possible to rotate with zero angular momentum

Answer 14

In divers, they move their arms away from their bodies and this gives another component relative to body which allows body to twist. Due to arm and body twisting

Question 15

Difference between internal and external forces

Answer 15

Internal forces both the equal and opposite reactions in body (equal to zero and cant move body)
External forces equal and opposite reactions in different bodies (doesnt have to equal zero and can change movement of body)

Question 16

Give examples of Internal and External forces

Answer 16

Internal forces - muscle forces and ligament forces

External forces - weight and contact forces

Question 17

What are contact forces

Answer 17

Arise from contact between two bodies and can be divided into normal forces and parallel forces

Question 18

What are normal contact forces

Answer 18

Perpindicular to contact surface

Question 19

What are parallel contact forces

Answer 19

Arise from friction between surfaces (move sideways)

Question 20

What is dynamic friction

Answer 20

Friction between two bodies moving relative to eachother and must be in opposite direction of motion

Question 21

What is static friction

Answer 21

Friction between two bodies not moving relative to eachother. Can be in any direction but no movement and is always larger than dynamic friction

Question 22

State the three axis of ground reaction forces

Answer 22

Vertical - Z
Horizontal
Antiposterior - Y
Mediolateral - X

Question 23

What is torque

Answer 23

The turning effect of force

Question 24

What direction does torque go

Answer 24

perpindicular to the plane of motion, or in the same direction as the resulting angular acceleration

Question 25

When do you use the work/energy equation and the impulse/momentum equation

Answer 25

work/energy when you have force acting on a distance

impulse/momentum when you have force acting over time

Question 26

What is work

Answer 26

Change in energy

Question 27

What are the three types of energy

Answer 27

Potential energy, elastic energy and kinetic energy

Question 28

What is power

Answer 28

rate of doing work, can find work under a power time curve

Question 29

Trade offs in energy

Answer 29

Something in air gravitational energy, something moving kinetic energy and bending elastic energy.

Question 30

What is the inverted pendulum

Answer 30

Inverted pendulum is the walking model and energy stays relative constant, when you increase gravitational energy you decrease kinetic energy and vice versa.

Question 31

What is the mass spring

Answer 31

Mass spring is the running model is where both kinetic and gravitational energy increases and decreases at the same time for large increases of energy

Question 32

What are concentric and eccentric movements

Answer 32

Concentric are positive contractions of muscles. Positive power is concentric.
Eccentric are negative contractions of muscles. Negative power is eccentric.

Question 33

What do moments (torque) tell you regarding gait?

Answer 33

Torque can tell you what muscle groups are being used the most.

Question 34

What do power at the joints tell you?

Answer 34

Positive power is concentric.

Negative power is eccentric

Question 35

What is stress

Answer 35

Internal force divided by the cross-sectional area (CSA) of the surface. A force over a small CSA increases stress and a force over a large CSA decreases stress

Question 36

What is tensile stress

Answer 36

Axial stress that occurs perpendicular to plane as a result from a pulling force

Question 37

What is compressive stress

Answer 37

Axial stress that occurs perpendicular to plane as a result from a pushing force

Question 38

What is shear force

Answer 38

Transverse stress that occurs parallel to plane as a result of parallel forces

Question 39

What is strain

Answer 39

Quantification of deformation of an object

Change in length/original length

Question 40

What is young’s modulus

Answer 40

The measure of stiffness of a solid material

Question 41

What is Wolff’s law

Answer 41

Bone in a healthy person will adapt to the loads under which it is placed to compromise.