Chapter 3 - Kinetics Concepts

Question 1

Basic Concepts Related to Kinetics:
What is the unit for mass?

Answer 1

kilogram (kg)

Question 2

Basic Concepts Related to Kinetics:
What is the formula for force (N)?

Answer 2

mass (kg) x acceleration (m/s^2)

Question 3

Basic Concepts Related to Kinetics:
What is the formula for weight (N)?

Answer 3

mass (kg) x acceleration (m/s^2)

Question 4

Basic Concepts Related to Kinetics:
What is the formula for pressure (Pa)?

Answer 4

force (N) / area (cm^2)

Question 5

Basic Concepts Related to Kinetics:
What is the unit for volume?

Answer 5

m^3

Question 6

Basic Concepts Related to Kinetics:
What is the unit for density?

Answer 6

(kg/m^3)

Question 7

Basic Concepts Related to Kinetics:
What is inertia?

Answer 7

• tendency to resist change in state of motion
• proportional to mass
• has no units

Question 8

Basic Concepts Related to Kinetics:
What is centre of gravity?

Answer 8

• point around which a body’s weight is equally balanced in all directions
• point that serves as an index of total body motion
• point at which the weight vector acts
• same as the centre of mass

Question 9

Basic Concepts Related to Kinetics:
What is torque?

Answer 9

The product of force and the perpendicular distance from the force’s line of action to the axis of rotation (T = Fd)

Question 10

Basic Concepts Related to Kinetics:
What is impulse?

Answer 10

• The product of force and the time during which the force acts (Ft)
• Units are Ns

Question 11

Mechanical Loads:
What is compression?

Answer 11

Pressing or squeezing force directed axially through a body
↓
↑

Question 12

Mechanical Loads:
What is tension?

Answer 12

Pulling or stretching force directed axially through a body
↑
↓

Question 13

Mechanical Loads:
What is shear?

Answer 13

Force directed parallel to a surface
→
←

Question 14

Mechanical Loads:
Example of shear

Answer 14

During the landing from a (ski) jump, the axial impact force at the knee includes a component of anteriorly directed shear on the tibial plateau, increasing stress on the ACL.

Question 15

Mechanical Loads:
What is stress?

Answer 15

• force per unit of area over which the force acts
• commonly used to describe force distribution within a body
• units are N/m^2
  ↓ ↓

Question 16

Mechanical Loads:
What is bending?

Answer 16

Asymmetric loading that produced tension on one side of a body’s longitudinal axis and compression on the other side.
→
←
→

Question 17

Mechanical Loads:
What is torsion?

Answer 17

Load producing twisting of a body around its longitudinal axis
↻
↺

Question 18

Effects of Loading:
What is deformation?

Answer 18

Change in shape (refer to graph)
- Elastic region
- Yield point
- Plastic region
- Ultimate failure point

(if force applied exceeds elastic limit, some deformation is permanent)

Question 19

Effects of Loading:
What is repetitive?

Answer 19

Repeated application of a subacute load that is usually of relatively low magnitude

(Loading over a period of time produces chronic injury - microtrauma)

Question 20

Effects of Loading:
What is acute?

Answer 20

Application of a single force of sufficient magnitude to cause injury to a biological tissue

(Single traumatic force injures tissues - macrotrauma)

Question 21

Effects of Loading:
What is the relationship between repetitive vs acute loading for likelihood of injury?

Answer 21

Graph
↑ Load magnitude (y-axis)
Likelihood of injury goes down exponentially
→ Frequency of loading (x-axis)

Question 22

Tools for Measuring Kinetic Quantities:
What is Electromyography (EMG)?

Answer 22

To study neuromuscular function

Question 23

Tools for Measuring Kinetic Quantities:
What is Dynamography?

Answer 23

• Force and pressure platforms interfaced with computer measure ground reaction forces
• Primarily employed in gait research, starts, takeoffs, landings, baseball & golf swings, and balance