Chapter 2 Introduction to biomechanics

Question 1

Motion and linear motion and angular motion

Answer 1

Motion:
Motion refers to the change in position of a body in relation to time

Linear motion:
Linear motion is motion that occurs either in a straight line or curved path

Angular motion:
Angular motion takes place when a body moves along a circular path

Question 2

Mass

Answer 2

Mass is the quantity of matter found within a particular body

Question 3

Inertia

Answer 3

Inertia can defined as the tendency for a body to resist a change in its state of motion, whether that state is at rest or moving with a constant velocity

Question 4

Velocity

Answer 4

Velocity is the rate of speed an object moves its position

Question 5

Force

Answer 5

Force is defined as a push or a pull

It can affect objects in two ways:
1) Change the shape of the object
2) Move the object

Force = Mass x acceleration

Question 6

Momentum

Answer 6

Momentum is equal to the mass of the object multiplied by its velocity

Mass x velocity

The higher the mass the higher the velocity, the greater the momentum will be

If two objects have the same mass, then the object with the greater velocity will have a greater momentum

Similarly, if two objects have the same velocity the object with the greater mass will have the greater momentum

Question 7

Force summation

Answer 7

Force summation is the correct timing and sequencing of body segments and muscles through a range of motion

Question 8

Simultaneous force summation

Answer 8

Simultaneous force summation is the use of of multiple body parts at the same time to produce force

Question 9

Sequential force summation

Answer 9

Sequential force summation is the activation of body parts that are used in sequence to produce force

Sequential force summation is more successful, and produces the maximal amount of force, if a number of principles are adhered to:
- Activating the stronger muscles first

• Using as many body parts as possible, enabling force to be generated over a greater time
• Transferring momentum from one body part to another when at maximum velocity
• The presence of a stable base for maximal acceleration of body parts to occur so that momentum can be transferred successfully form one body part to another
• Ensuring appropriate follow-through is used to prevent unnecessary deceleration of body parts

Question 10

Moment of inertia

Answer 10

Moment of inertia is a measure of an object’s resistance to change in its rate of rotation

Question 11

Angular momentum

Answer 11

Angular momentum is the path of momentum that is in a circle

Question 12

Angular distance

Answer 12

Angular distance is measured in degrees and measures the number of degrees an object passes through from start to finish

Question 13

Angular displacement

Answer 13

Angular displacement is measured in degrees and measures the number of degrees the object moves from the starting point

So, an object that rotates twice has displacement of 0degrees

Question 14

Angular speed

Answer 14

Angular speed is the measure of how quickly angular distance is covered

This is calculated by the angle divided by time involved in the activity

So, if it took four seconds to complete two rotations then the angular speed is 180 degrees per second

Question 15

Angular velocity

Answer 15

Angular velocity is the measure of how quickly the object has move from tis starting point and in what direction it has moved

Question 16

Angular acceleration

Answer 16

Angular acceleration is the measure of the rate of change of angular position

Question 17

Impluse

Answer 17

Impulse is the change in momentum in an object

Impulse = force x time

Question 18

Newton’s first law

Answer 18

Law of inertia:
A body will remain at rest or in uniform in a straight line unless acted upon by an external force

Question 19

Newton’s second law of motion

Answer 19

The law of force and acceleration:
A force applied to an object will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of the force

Question 20

Newton’s third law of motion

Answer 20

The law of action-reaction:
When two objects come in contact with one another, they exert forces that are equal in size but opposite in direction on each other - for every action there is an equal and opposite reaction

Question 21

Torque

Answer 21

Torque is the rotational force (push or pull) that makes an object rotate

Question 22

Levers

Answer 22

Levers refer to a beam or rigid structure that rotates around an axis

The axis is the turning point of the lever

Question 23

First class lever

Answer 23

First class levers have the axis as the central component that separates the force and resistance

Question 24

Second class lever

Answer 24

Second class levers have the resistance as the central component that separates the axis and the force

Question 25

Third class levers

Answer 25

Third class levers have the force as a central component that separates the axis and resistance

Question 26

Equilibrium

Answer 26

Equilibrium refers to the state in which there is a balance of forces or influences in opposition to each other

Question 27

Static equilibrium

Answer 27

Is the state in which a body has zero velocity and zero acceleration A body is in equilibrium when the sum of all forces and sum of all moments acting on the body are zero

Question 28

Dynamic equilibrium

Answer 28

Is the state in which the body is in motion with a constant velocity

Question 29

Stability

Answer 29

Stability refers to the degree to which a body resists changing its equilibrium

Question 30

Balance

Answer 30

Balance is the ability to control the state of equilibrium

Question 31

Centre of gravity

Answer 31

COG is the central point of an object, where all of its weight is evenly distributed and balanced This point shifts with every movement of the body

Question 32

How to increase stability and balance

Answer 32

Lowing an object COG Ensuring the line of gravity is over the base of support Increasing the size of the base of support Increasing the friction between two or more bodies Increasing the mass of an object Extending the base of support in the direction from which a force is coming