MOTION AND

NEWTON'S LAWS

MOTION AND NEWTON'S LAWS

Definition

Motion is a change of

position or place of object

or subject in relation to a

fixed point or a reference

point.

Body motion is produced

or started by some action

of muscular system.

Types of motion

1. Linear or translatory

motion

2. Angular or rotatory

motion

3. General motion

Distance :

Is a scalar quantity (having magnitude only).

Displacement:

Is a vector quantity (having magnitude and

direction).

Velocity:

Is a displacement divided by the time.

Speed:

Is a distance divided by the time.

1. Linear or translatory

motion

It is a motion in which any given point of the body moves along a straight line or a curved line

:All parts of the body travels

Same Distance

Same direction

In the same time

1. Linear or translatory

motion

Rectilinear Motion

Curvilinear

Motion

Rectilinear Motion

Each point of the segment moves in straight lines with:

Same linear displacement

Same linear velocity

Curvilinear Motion

Each point of the segment moves in curved lines with:

Nearly same linear displacement

Same linear velocity

2. Angular or rotatory

motion

Angular motion of any segment is rotation of this segment around a central imaginary line oriented perpendicular to the plane of

rotation called an axis of rotation. (rotation around an axis)

2. Angular or rotatory

motion

In angular motion each point of the segment travels through:

Same angular displacement

Different linear displacement

Same angle

Same direction

In the same time

The linear displacement depends on the length of the segment.

For example: if a tall and short subjects take the same angle ofhip movement during walking.

3. General motion

It is a combination between linear and angular motion.

For example: During walking and when the diver fall linearly

downward.

• Sports exercises : cumulative angular

motion of the joints imparts linear motion

to a thrown object (ball, shot) or to an

object struck with an instrument (bat,

racket)

NEWTON'S LAWS

The laws of motion constitute the

fundamental principles of statics, kinetics,

and kinematics.

Newton's laws of motion have many

applications to physical education

activities and sports.

The law states that:

Every body remains at rest or in

uniform motion at a constant velocity

until any force acts upon it to cause

any change

FIRST NEWTON'S LAW

Law of Inertia

Inertia

Inertia is a resistance of the body to any thing that tries to change its state of rest or motion

Types of inertia

Moving inertiaResting inertia

Inertia is directly proportional to the mass

Inertia

• The greater an object’s mass, the greater its inertia.

– the greater the mass, the more force needed to

significantly change an object’s inertia.

• Examples

– Sprinter in starting blocks must apply

considerable force to overcome his resting

inertia.

– Runner on an indoor track must apply

considerable force to overcome moving inertia &

stop before hitting the wall.

– Thrown or struck balls require force to stop

them.

Force is required to change

inertia

Any activity carried out at a

steady pace in a consistent

direction will conserve

energy.

Any irregularly paced or

directed activity will be very

costly to energy reserves.

Ex. handball & basketball

are so much more fatiguing

than running in a regular

speed

Resting inertia

The inertia of the body during rest

Clinical application:

Hanging

The sudden movement of thebody while the head is fixedwill cause dislocation of theatlanto-axial jointaccompanied by tearing of thetranseverse ligament.

Moving inertia

The inertia of the body during motion

Clinical application:

Whip lash injury (cervical syndrome)

When the car stops suddenly the trunk

will be fixed by the belt but the head is

still moving forward with the same

velocity of the car by the effect of moving

inertia . This will lead to fracture

dislocation of the atlanto-axial joint, but

without tearing of the transeverse

ligament so the subject will be alive

Law of Acceleration

SECOND NEWTON'S LAW

The law states that:

Acceleration produced by a force acting on the

body is directly proportional to the magnitude of

the force and inversely proportional to the mass of

the body and the movement occurs in the same

direction of the applied force.

Acceleration -: the rate of change in velocity

Change of velocity=AccelerationTime

a α fm

Force (F) = Mass (m)× Acceleration (a)

To attain speed in moving the body, a strong

muscular force is generally necessary

A much greater force is required from the

muscles to accelerate a 230-pound man than

than to accelerate a 130-pound man to the same

running speed

A baseball may be accelerated faster than a shot

because of the difference in weight

The force required to run at half speed is less

than the force required to run at top speed

To impart speed to a ball or an object, the body

part holding the object must be rapidly

accelerated

Law of reaction

THIRD NEWTON'S LAW

The law states that:

For every action there is an equal and opposite

reaction equal in magnitude and opposite in

direction

Clinical application

1. During standing on a hard surface

2. During walking

3. During push up exercises