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Uni Biomechanics > Linear Kinetics & Angular Kinetics > Flashcards

Linear Kinetics & Angular Kinetics Flashcards

1
Q

What are the two branches of kinetics?

A

Static - a condition in which a body/object is at rest.

Dynamic - a condition in which a body/ object is in motion.

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2
Q

Define force.

A

The pushing or pulling action this body has (Newtons).

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3
Q

Define net force

A

The resultant of all forces affecting an object.

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4
Q

When does equilibrium exist?

A
  • the net force on a body is zero.

- the resultant of all forces acting upon the object is zero.

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5
Q

Define an internal force.

A

Force acting within the system under investigation.

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6
Q

Define external force.

A

Force acting on a system due to the interaction with its environment.

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7
Q

What 5 things is force characterised by?

A
  • magnitude
  • rate of development
  • contact time
  • frequency of application
  • location of application
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8
Q

Define mass.

A

Amount of matter in a body (constant value).

Measure of the inertia of a body (measured in kg).

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9
Q

Define inertia.

A

The resistance of a body to change motion.

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10
Q

Define weight.

A
  • the gravitational force attracting a body towards the earth.
  • measured in Newtons.
  • different to mass (varies).
  • weight is a force and is directly related to mass.
  • weight (W) = mass (m) x gravity (g)
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11
Q

What is the force exerted by gravity?

A

9.81 m/s2

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12
Q

Define momentum.

A

The quantity of motion (linear or angular)

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13
Q

Give the equation of linear momentum.

A

Linear momentum = Mass (m) x Linear Velocity (v)

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14
Q

What is force application affected by?

A

Mass and weight of a performer.

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15
Q

Define impulse.

A

The product of force and the time over which force is applied.

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16
Q

Give the equation for impulse.

A

Impulse = Force (F) x time (t)

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17
Q

Define kinetics.

A
  • The branch of mechanics that deals with the causes of motion.
  • Concerned with the forces that act on a system.
  • Basis for understanding kinetics is the concept of force.
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18
Q

Why investigate kinetics?

A
  • explains underlying cause of the movement pattern of technique.
  • provides an explanation of the musculoskeletal demand of movement
19
Q

Application of kinetics.

A

Informs the coach in terms of overload AND specificity.

  • key for effective skill development.
  • key for effective strength and conditioning.
20
Q

What does net magnitude depend on?

A

Horizontal and vertical force

21
Q

Name and explain Newton’s 1st law.

A

Law of inertia.
Every body continues in its state of rest or motion in a straight line unless compelled to change that by forces exerted upon it.

22
Q

Name and explain Newton’s 2nd Law.

A

Law of acceleration.
The rate of change of momentum of a body is directly proportional to the force causing it and the change takes place in the direction in which the force acts.

23
Q

Name and explain Newton’s 3rd law.

A

Law of action-reaction.

To every action there is an equal and opposite reaction.

24
Q

Define work.

A
  • Product of a force applied on a body and the distance the body moves in that direction in that time.
  • Work = force x distance
  • measured in Joules (J)
25
Q

Define power.

A
  • The rate at which a force does work.
  • power = work/time
  • power = force x velocity
  • measured in Watts (W)
26
Q

Define energy.

A

The capacity to do work.

Measured in Joules (J).

27
Q

What is used to measure external forces?

A

Dynamometers e.g load cells, force plates, instrumented equipment.

28
Q

Define load cell.

A

A transducer that is used to create an electrical signal whose magnitude is directly proportional to the force being measured.

29
Q

What are the 3 phases of the counter-movement jump?

A
  1. Preparation for take off
  2. Flight
  3. Impact/landing
30
Q

When does max GRF occur?

A

Early in the push off phase

31
Q

What is the formula for the rate of force development (RFD)?

A 
RFD = Fp/t 
Fp = peak force
32
Q

What is the formula for jump height (m)?

A

h=1/2gt2

33
Q

During a penalty kick, a footballer applies an average force of 102N to a 0.4kg ball for a duration of 0.12s. What is the impulse applied to a ball and the velocity of the ball?

A 
Impulse = 12.24 N/s
Velocity = 30.6 N/kg/s
34
Q

Define angular kinetics.

A

Branch of mechanics that deals with the causes of angular motion

35
Q

Define torque.

A

A tendency of a force to cause a rotation about an axis.

36
Q

Define eccentric force.

A

A force that does not act through the pivot point.

37
Q

Define moment (torque) arm.

A

The perpendicular distance between the force and pivot.

38
Q

What is the formula for torque?

A

T=F•d

39
Q

Give examples of moments of force in sport.

A

Muscle force.
GRF.
Gravitational force.

40
Q

What is a force couple?

A
  • a pair of forces
  • equal in magnitude
  • opposite in direction
  • cause rotation but not translation
41
Q

Define equilibrium.

A

Sum of the clockwise moments = sum of the anti-clockwise moments

42
Q

Define Moment of inertia.

A

The resistance of a body to change in angular motion.

Dependant on mass distribution about an axis of rotation.

43
Q

What is the formula for moment of inertia?

A

I=m•r2

44
Q

What is angular impulse?

A

Angular Impulse = rate of change in angular momentum

Uni Biomechanics (6 decks)

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