Linear Kinetics & Angular Kinetics

Question 1

What are the two branches of kinetics?

Answer 1

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

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

Question 2

Define force.

Answer 2

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

Question 3

Define net force

Answer 3

The resultant of all forces affecting an object.

Question 4

When does equilibrium exist?

Answer 4

• the net force on a body is zero.

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

Question 5

Define an internal force.

Answer 5

Force acting within the system under investigation.

Question 6

Define external force.

Answer 6

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

Question 7

What 5 things is force characterised by?

Answer 7

• magnitude
• rate of development
• contact time
• frequency of application
• location of application

Question 8

Define mass.

Answer 8

Amount of matter in a body (constant value).

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

Question 9

Define inertia.

Answer 9

The resistance of a body to change motion.

Question 10

Define weight.

Answer 10

• 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)

Question 11

What is the force exerted by gravity?

Answer 11

9.81 m/s2

Question 12

Define momentum.

Answer 12

The quantity of motion (linear or angular)

Question 13

Give the equation of linear momentum.

Answer 13

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

Question 14

What is force application affected by?

Answer 14

Mass and weight of a performer.

Question 15

Define impulse.

Answer 15

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

Question 16

Give the equation for impulse.

Answer 16

Impulse = Force (F) x time (t)

Question 17

Define kinetics.

Answer 17

• 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.

Question 18

Why investigate kinetics?

Answer 18

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

Question 19

Application of kinetics.

Answer 19

Informs the coach in terms of overload AND specificity.

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

Question 20

What does net magnitude depend on?

Answer 20

Horizontal and vertical force

Question 21

Name and explain Newton’s 1st law.

Answer 21

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.

Question 22

Name and explain Newton’s 2nd Law.

Answer 22

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.

Question 23

Name and explain Newton’s 3rd law.

Answer 23

Law of action-reaction.

To every action there is an equal and opposite reaction.

Question 24

Define work.

Answer 24

• 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)

Question 25

Define power.

Answer 25

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

Question 26

Define energy.

Answer 26

The capacity to do work. | Measured in Joules (J).

Question 27

What is used to measure external forces?

Answer 27

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

Question 28

Define load cell.

Answer 28

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

Question 29

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

Answer 29

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

Question 30

When does max GRF occur?

Answer 30

Early in the push off phase

Question 31

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

Answer 31

``` RFD = Fp/t Fp = peak force ```

Question 32

What is the formula for jump height (m)?

Answer 32

h=1/2gt2

Question 33

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?

Answer 33

``` Impulse = 12.24 N/s Velocity = 30.6 N/kg/s ```

Question 34

Define angular kinetics.

Answer 34

Branch of mechanics that deals with the causes of angular motion

Question 35

Define torque.

Answer 35

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

Question 36

Define eccentric force.

Answer 36

A force that does not act through the pivot point.

Question 37

Define moment (torque) arm.

Answer 37

The perpendicular distance between the force and pivot.

Question 38

What is the formula for torque?

Answer 38

T=F•d

Question 39

Give examples of moments of force in sport.

Answer 39

Muscle force. GRF. Gravitational force.

Question 40

What is a force couple?

Answer 40

- a pair of forces - equal in magnitude - opposite in direction - cause rotation but not translation

Question 41

Define equilibrium.

Answer 41

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

Question 42

Define Moment of inertia.

Answer 42

The resistance of a body to change in angular motion. | Dependant on mass distribution about an axis of rotation.

Question 43

What is the formula for moment of inertia?

Answer 43

I=m•r2

Question 44

What is angular impulse?

Answer 44

Angular Impulse = rate of change in angular momentum