Kinematic Concepts of Human Movement (Chapter 4)

Question 1

Kinetics

Answer 1

Studies motion and the forces that underlie this motion.

Question 2

kinematics

Answer 2

is solely focused on the study of motion not taking into account forces that may be acting upon the body in motion.

Question 3

General motion

Answer 3

Combination of linear and angular motion, nearly all human movement is an example of general motion

Question 4

Linear motion

Answer 4

movement where all body parts move at the same speed in the same direction.

Question 5

Angular motion

Answer 5

rotation around the central axis or a fixed point

Question 6

projectile motion

Answer 6

an object or body being acted upon when airborne

Question 7

rectilinear

Answer 7

movement is along a straight path

Question 8

curvilinear

Answer 8

Movement is along a curved path

Question 9

Distance vs displacement

Answer 9

Both measure how far a body has travelled and can be used to describe motion, depending on which will provide the most useful information

• distance: measures the path travelled from start to finish (400m=400)
• displacement: is the change in position (how far it is from initial to final position)

Question 10

Speed

Answer 10

distance (length of path) divided by time

Question 11

velocity

Answer 11

displacement divided by time

Question 12

Acceleration

Answer 12

a change in velocity in a given period of time.

A= final velocity-initial velocity / time
measured in m/s2

Acceleration can be either positive or negative (speeding up or down)
positive acceleration- sprinter out of the blocks
negative acceleration - bike rider maintaining balance around a corner

if acceleration equals 0, this doesnt mean the subkect is stationary, there is just no change in velocity. cross country through middle part of race trying to maintain pace.

Question 13

angular motion

Answer 13

involves the rotation of a body around a central axis or a fixed point.

this can be seen in humans limbs around joints.
e.g running, leg rotates around hip axis (angular motion of the limbs results in linear motion of the whole body)

the axis rotation can be real or imaginary, internal/external depending on the positioning of the body.
AN external axis could be the centre of gravity when performing a tuck roll or the bar in gymnastics

Question 14

Torque (what is it and how can it be increased)

Answer 14

Angular motion is created by a force that does not act through an objects centre of gravity that causes rotation.

torque can be calculated by multiplying the force applied by the lever. (force x lever arm)

how can it be increased:
- size of force applied (greater = increased torque)
- length of lever arm- longer lever arm = greater torque.

Question 15

Angular motion- distance and displacement

Answer 15

angular distance: measures the path travelled from start to finish

Angular displacement: measures change in position how far from the start position is the finish

e.g gymnast completed 1 1/2 giant on the bar, distance would be 540C and displacement would only be 180

Question 16

Angular speed

Answer 16

angular distance covered divided by the time taken.
900/4sec= 225/sec

Question 17

Angular velocity

Answer 17

angular displacement divided by the time taken
e.g
180/4sec= 45/sec

Question 18

Angular acceleration

Answer 18

a change in angular velocity in a given period of time

final velocity- initial velocity/time

can either be pos/neg/0
measured in degrees

300-100/s/0.5sec= 400 per sec

Question 19

Newton’s laws of Angular motion

Answer 19

First law: angular momentum of a body remains constant unless acted upon by an external torque

Second law: a torque applied to an object will produce a change in angular motion in the direction of the applied torque that is directly proportional to the size of the torque and inversely proportional to the moment of inertia of the object.

Third: for every torque, there is an opposite and equal torque

Question 19

Newton’s laws of Angular motion

Answer 19

First law: angular momentum of a body remains constant unless acted upon by an external torque

Second law: a torque applied to an object will produce a change in angular motion in the direction of the applied torque that is directly proportional to the size of the torque and inversely proportional to the moment of inertia of the object.

Third: for every torque, there is an opposite and equal torque

Question 20

Angular momentum

Answer 20

the amount of angular motion possessed by an object is known as its angular momentum

Angular momentum is the product of the moment of inertia and the angular velocity (moi x av)

it is dependent on both:
- the mass of the rotating object or body (increased mass=increased moi)
- the distance the weight is distributed from the axis of rotation (mass further away from axis= increased moi)

Question 21

moi

Answer 21

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

Question 22

how to increase angular velocity

Answer 22

reduce moment of inertia (diver tucking in)

layout of pike (increasing moi) to slow down

Question 23

Conservation of angular momentum

Answer 23

Conserved when body is in flight and can be best observed through diving, gym and trampolining

when angular momentum is being conserved there is a trade off between angular velocity and moi.

-decreased moment of inertia results in reater angular velocity
-an increased moi results in a decreased angular velocity

Question 24

Projectile motion (what is it, factors affecting it )

Answer 24

Anything launched into the air (only influenced by gravity and air resistance) becomes a projectile (even humans)

both verticle and horizontal component

vertical component: influenced by gravity and vertical component of the initial projection velocity.

Acceleration due to gravity is constant for any object, regardless of the size shape or weight ignoring the effects of air resistance.
Horizontal component influenced by air resistance.

Question 25

Factors affecting flight path of a projectile

Answer 25

angle of release
speed of release
height of release

Question 26

Angle of release

Answer 26

the angle at which the object is projected into the air, in relation to the horizontal

the flight path could be:
vetical: an object goes straight up and down (rebounding in basketball)

Parabolic: occurs when angle is between 0-90* (release angle at 45* will result in the greatest horizontal distance covered) - diff angles depend on where the target is.

Horizontal: opject is released at 0*

Question 27

Speed of release

Answer 27

the speed at which an object is thrown/hit/kicked/propelled into the air
-vertical component determines height and flight time, horizontal component determines horizontal distance

• the greater the speed of release, the greater the horizontal range of the projectile

Question 28

Height of release

Answer 28

the difference between the height that a projectile is released from and the height at which it lands.

if height of release is 0 (ie. projection height and landing height are both equal) optimal angle of release = 45*

If height of release is greater 0(ie. projection height is above landing height) optimal angle of release= less than 45*

If height of release is less than 0 (ie. projection height is below landing height) optimal angle of release=greater than 45*