# Linear motion

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- Created by: staffy_rose
- Created on: 07-06-18 17:42

Linear motion

Movement of a body in a straight or curved line where all parts move the same distance, in the same direction over the same time

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Direct force

a force applied through the centre of mass resulting in linear motion

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Centre of mass

the point at wich a body is balanced in all directions.

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Distance

the total length covered from start to finish positions

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Displacement

the shortest straight-line route from start to finish positions

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Speed

the rate of change in distance (m/s) calculated using Distance/Time

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Velocity

the rate of change in displacement (m/s) calculated using Displacement/Time Taken

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Acceleration

the rate of change in velocity (m/s/s) calculated using final velocity-initial velocity/time taken

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Deaccleration

the rate of change in velocity (decrease or negative) (m/s/s)

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Distance/time graph

- a visual representation of the distance travelled plotted against time taken

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Gradient

the slope of a graph at a particular moment in time. Gradient= change in y/change in x

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Speed/time graph

A visual representation of the speed of moy

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Angular motion

movement of a body or body part in a circular path about an axis of rotation

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Torque

a measure of the turning force applied to a body

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Longitudinal axis

runs from head to toe through the centre of mass. E.g full turn in trampolining

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Transverse axis

runs from left to right through the centre of mass. E.g somersaults in trampolining

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Frontal axis

runs from front to back through the centre of mass. E.g cartwheels in gymnastics

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Angular motion descriptors

Angular velocity, moment of intertia, angular momentum

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Angular velocity

the rate of change in angular displacement measured in radians per second

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Moment of inertia

the resistance of a body to change its state of angular motion or rotation.

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Factors that affect moment of inertia

1. Mass. The greater the mass of the body, the greater the moment of inertia and vice versa. Diving and gymnastics are usually performed by athletes with a low mass.

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Factors that affect moment of inertia 2

2. Distribution of mass. The furthur the mass moves from the axis of rotation, the greater the moment of inertia. Movements where the mass is tucked in around the axis of rotation e.g a tucked somersault, lower the moment of inertia.

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Angular momentum

the quantity of angular motion posessed by a body

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Conservation of angular momentum

Angular momentum cannot be changed once in flight so as much of it has to be generated before take off. The performer can then manipulate moment of inertia to maximise performance by including twists, spins to gain technical points

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Air resistance

the force that opposes the direction of motion of a body through the air

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Drag

the force that opposes the direction of motion of a body through water

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Streamlining

the creation of smooth air flow around an aerodynamic shape

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Aerofoil

a streamlined shape with a curved upper surface and flat lower surface designed to give an additional lif force to the body

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Factors that affect the scale of air resistance and drag

1. Velocity- the greater the velocity, the greater the air resistance or drag. E.g Track cycling is greatly affected due to the high velocities travelled.

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Factors that affect the scale of air resistance and drag

2. Frontal cross sectional area- the larger it is the larger the air resistance or drag. E.g Cycling is greatly affected due to the large frontal cross section of the body facing oncoming air.

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Factors that affect the scale of air resistance and drag

3. Streamlining and shape- the more streamline the body, the lower the air resistance. Many sports use tear drop shapes in cyclists helmets.

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Factors that affect the scale of air resistance and drag

4. Surface characteristics- the smoother the surface, the lower the air resistance or drag. E.g swimmers wear specially engineered clothing to create the smoothest surface possible to reduce the friction between the fluid and the body surface.

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Projectile motion

movement of a body through the air following a curved flight path under the force of gravity

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Projectile

a body that is launched into the air losing contact with the ground surface such as the discus

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Factors that affect the horizontal distance travelled by a projectile

1. Speed of release- Newtons 2nd Law- acceleration- the greater the force applied to the projectile, the greater the change in momentum and therefore acceleration.

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Factors that affect the horizontal distance travelled by a projectile

2. Angle of release- at 90* the projectile will accelerate vertically upwards and come straight back down. 45*= optimal angle to maximise distance. Anything below 45* the projectile doesnt achieve sufficient height to maxmise flight time.

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Factors that affect the horizontal distance travelled by a projectile

2. Anything above 45* up to 90*- the projectile reaches peak height too quickly and rapidly returns to the ground

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Factors that affect the horizontal distance travelled by a projectile

3. Height of release- 45* is optimal angle of release. Where the release height is above the landing height e.g in shot put, the optimal angle of release is less than 45* as the projectile already has increased flight time due to the increased height

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Factors that affect the horizontal distance travelled by a projectile

3. Where the height of release is below the landing height e.g bunker shot in golf, the optimal angle of release is more than 45* as the projectile needs increased flight time to overcome the obstacle.

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Parabolic flight path- E.g Shot put

if weight is the dominant force and air resistance is small. The flight path has a symmetrical shape

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Non-parabolic flight path- E.g badminton shuttle

if air resistance is the dominant force and weight is small. The flight path is asymmetrical (unequal)

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Bernoulli principle

creation of an additional lift force on a projectile in flight resulting from Bernoullis conclusion that the higher the velocity of air flow, the lower the surrounding pressure.

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Lift force

an additional force created by a pressure gradient forming on opposing surfaces of an aerofoil moving through a fluid

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Magnus effect

creation of an additional Magnus force on a spinning projectile which deviates from the flight path

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Magnus force

a force created from a pressure gradient on opposing surfaces of a spinning body moving through the air

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Hook

a type of sidespin used to deviate a projectiles flight path to the left

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Slice

a type of sidespin used to deviate a projectiles flight path to the right

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## Other cards in this set

### Card 2

#### Front

Direct force

#### Back

a force applied through the centre of mass resulting in linear motion

### Card 3

#### Front

Centre of mass

#### Back

### Card 4

#### Front

Distance

#### Back

### Card 5

#### Front

Displacement

#### Back

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