LINEAR AND ANGULAR CONCEPTS OF HUMAN MOVEMENT Flashcards
(26 cards)
Types of motion
The term motion refers to a body’s change in position in relation to time. Motion can be linear or angular (or a combination of these in the case of general motion) and relates to both living (animate) and non-living (inanimate) bodies.
- Humans and animals are examples of animate bodies, while a baseball is an example of an inanimate body.
Linear motion
commonly referred to as translation, takes place either in a straight line or curved path. Movement in a straight line is referred to as rectilinear motion, where all parts of a body travel the same distance, in the same direction, at the same time (e.g. a young child sledding down a mountain on a toboggan).
- Movement over a curved path is referred to as curvilinear motion (e.g. the path of a ball thrown through the air until gravity forces it to the ground).
Angular motion
Commonly referred to as rotation, occurs when a body moves along a circular path at the same angle, in the same direction, at the same time. Angular motion occurs around some type of axis, which can be either external or internal.
- An example of an external axis in sport is a gymnast rotating around a high bar, while an internal axis would be a joint in the body around which a body part rotates.
key angular and linear concepts
Mass
- inertia and moment of inertia
- force and torque
- speed, velocity, acceleration and angular speed, velocity and acceleration
- momentum and angular momentum
- impulse
mass
The term mass is used to describe the quantity of matter found within a particular body. Mass is typically measured in kilograms. A person with a large mass is composed of large quantities of matter, while a person with a small mass is composed of a small quantity of matter.
- There is a direct relationship between the amount of mass an object has and its weight.
- Weight refers to the force that a body exerts on the ground and is found by multiplying mass and the acceleration of gravity.
Inertia
Inertia describes the reluctance of a body to change its state of motion; it is closely linked to an object’s mass.
- A body at rest may be reluctant to move, and a body that is moving may be reluctant to stop.
- An object with a small mass is able to change its state of motion more easily than an object with a large mass can
A ball with a small mass has less inertia and is easier to throw than a ball with a large mass and large inertia.
MASS V WEIGHT
mass - The term mass is used to describe the amount of matter an object is made up of. The units of mass are kilograms (kg)
weight - The term weight refers to the amount of force exerted on the body by gravity. The terms are often confused as body ‘weight’ is measured in kg. However, weight is measured in newtons (n)
Weight = mass x gravity
static inertia
includes the reluctance of a heavy piece of sports equipment to be moved, such as a barbell
Dynamic inertia
is the reluctance of a rugby player running quickly with the ball to be stopped (change of direction + velocity)
friction
—> friction will oppose motion
- In sport there are times when it is beneficial to decrease friction between two surfaces or to increase friction
- To overcome friction you must apply an increasingly greater force
force
—> Force is defined as a push or a pull, which can accelerate, decelerate and/or change direction of a body with mass.
- To change the state of a body, a force must be applied t it.
The formula is:
F = ma (Force = mass × acceleration)
force example
For example, a heavy barbell on the floor in a weightlifting competition will only be lifted if sufficient force is created to overcome its inertia
momentum
—> this is a measure of the amount of motion an object has and its resistance to changing that motion. It is a combination of mass and velocity
- The units of velocity are kg m/s
Equation: mass x velocity
Example: if an object has zero velocity (not moving), means they have zero momentum. The higher the mass and the higher the velocity, the greater the momentum will be
conservation of momentum
—> whenever two bodies collide, the combined momentum of the two bodies is conserved (stays the same)
Equation: Mv = mV
Example: tennis serve - all momentum from preparing for the serve moves the ball very quickly. All moments from one object will transfer to another.
summation of momentum
—> when the main aim of a sport is to hit, kick or throw an object or ball as far as possible, it is important that the object is released to struck with maximum velocity eg. Teeing off in golf
- In many instances a submaximal fore is the aim. Example free throw in basketball and being able to control the quantity of force generated is important sequential summation of momentum, which results in maximal force
impulse
Impulse is a change in momentum.
Impulse = force x time
We need to understand impulse, or changes in momentum, in two different ways.
- Momentum breakers decrease momentum (e.g. when a cricketer catches a ball or a gymnast lands on the mat after jumping off the beam).
- Momentum makers increase momentum (such as when a golfer drives a golf ball, or a footballer kicks a football).
linear speed
the average speed of a body refers to the distance covered divided by the time taken
- S = d/t (s = speed, d = distance, t = time)
- Metres per second (m/s)
linear velocity
measures the displacement an object experiences over time
- V = d / t (v = velocity, d = distance, t = time)
- Metres per second (m/s)
linear distance v displacement
distance refers to how much ground an object covers throughout its motion
- While displacement refers to an objects overall change of position from one point to another
linear acceleration
acceleration refers to the rate of velocity change experienced by an object overtime
Positive acceleration = speeds up (velocity increased)
Zero acceleration = velocity does not change over the period of time measured (remains constant). In diving the athlete would be moving at a constant acceleration due to external forces of gravity until they hit the water
Negative acceleration = slwoing down, measured in units m/s squared
Acceleration = change in velocity/change in time
angular distance v displacement
when a body rotates from one position to another, it experiences angular motion. The angular distance is the total of all angular changes that result from an object or body part angled between the starting and finishing position
- Example: the angular displacement of the ten-bowlers arm between these two positions (start of the forward swing of the ball and end position of arm after release) is 120 degrees, while the total angular distance the arm travels is 240 degrees
angular speed
refers to the angular distance covered, divided by the time taken
- O/s degrees per second
angular velocity
is the rate of change of the angular displacement of a body overtime
- O/s degrees per second
angular acceleration
this is the rate of change of angular velocity, or how quickly a body changes its angular position
- This can be positive, negative or zero. Zero acceleration means that angular velocity of the body is constant
- Measured in degrees per second squared (o/s squared)
