Week 1

Question 1

1. Law of Inertia

Answer 1

Body remains at rest or in a state of uniform motion in a straight line unless acted on by an unbalanced force
- Inertia is a property of an object that makes the object resist both the initiation of motion and change of motion (acceleration)

Question 2

Static equilibrium (law of inertia)

Question 3

Dynamic equilibrium (law of inertia)

Answer 3

moving at consistent speed
o Linear dynamic equilibrium
o Angular dynamic equilibrium

Question 4

2. Law of Acceleration

Answer 4

acceleration of an object is proportional to the unbalanced forces acting on it and inversely proportional to the mass of the object
A = force / mass
F = mass x acceleration (acceleration from no movement to any movement is proportional to force and direction that caused it)

Question 5

Force acceleration (LOA)

Answer 5

• Force Acceleration, Linear - More force is needed to accelerate heavier car to same speed
• Force Acceleration, Rotation – Torque, the ability of the force to cause rotation of the lever, force perpendicular to lever arm

Question 6

Moment Arm

Answer 6

shortest distance between the action line and the joint axis (perpendicular distance from the axis to the force vector)
T = F x perpendicular distance to axis, or moment arm

Question 7

Angular Motion

Answer 7

Angle of Application – angle between the application of force and fulcrum
* Optimal angle of pull to generate most torque (rotary force) is 90 degrees
*Any angle not 90 means not all of the force is rotational
* Longer segment makes it harder to move
tuck = fast, layout = slow

Question 8

Momentum (LOA)

Answer 8

• The time over which a force is applied
  
  • Slow app of force – low momentum
  • Quick app of force – high momentum
    F = mass x acceleration
    F = mass x (Velocity/Time)
    F x Time = Mass x Velocity
    F x Time = Momentum
  • Large force and Long time means high momentum

Question 9

Impulse (LOA)

Answer 9

Moment of impact

Question 10

Work and Energy (LOA)

Answer 10

• Work is force applied over a distance
  
  • Does not take time into consideration
• Process of transferring energy
  
  • Potential energy – stored energy
  • Kinetic energy – action taking place

Question 11

Power (LOA)

Answer 11

• Doing work with a specific time frame
  
  • Squat and jump have the same work, bc a jump takes less time is has more power
• Inverse relationship to time
  
  • Less time for movement – more power

Question 12

3. Law of Reaction

Answer 12

for every action there is an equal and opposite reaction
* Force always comes in pairs, equal in magnitude and opposite in direction

Question 13

Force Systems

Answer 13

1. Linear
2. Concurrent
3. Parallel

Question 14

Shear Forces

Answer 14

moves or attempts to move an object. Parallel to contacting surfaces and in the direction of the attempted movement

Question 15

Friction

Answer 15

this force potentially exists whenever two objects contact
- Will have magnitudes whenever the 2 objects try to slide on each other
- Comes in pairs, equal and opposite, applied to each contacting surface
- Direction of force of friction is always opposite the direction of movement

Question 16

Static vs Kinetic Friction

Answer 16

Static - maximal potential force (Frs) is the product of a constant value and the magnitude of the contact force

Kinetic Friction – once an object is in motion, friction is a constant value (Frk)
- Always smaller than the value for static friction

Question 17

Lever Components

Answer 17

• Lever – rigid bar revolving around a fixed point
• Fulcrum – axis, point of rotation
• Effort arm (Ea) – distance from the application of effort force to axis
• Resistance Arm (RA)- distance form application of resistance force to axis

Question 18

First Class Lever

Answer 18

axis in the middle (teeter totter, triceps at olecranon process)

Question 19

Second Class Lever

Answer 19

resistance in the middle (wheelbarrow, going up on toes)
- Efforts arm is always longer than resistance arm- advantageous for the effort force

Question 20

Third Class Lever

Answer 20

effort force is in the middle
- RA is always longer than the effort arm, favors ROM
- Most muscle systems in body

Question 21

Mechanical Advantage

Answer 21

Measure of the mechanical efficiency of a lever system
- Relative effectiveness or ease of the effort force to overcome the resistance

Mechanical Advantage = Effort Arm/Resistance Arm

• Mechanical advantage is >1 – easier to do
• Mechanical advantage is <1 – harder to do

Question 22

Parallel Force Systems

Answer 22

Two or more parallel force systems act on the same object but at some distance from each other

Action lines do not intersect
- Need to understand the principle of levers and torque