# OCR A2 P.E Biomechanics - Angular Motion

Everything you need to know about Angular Motion. Let me know if there is anything that needs editing or adding in. Thank you! I hope it helps

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Biomechanics ­ Angular Motion
Glossary
Angular Motion ­ Motion in a circular path about an axis of rotation. This is created by applying an
external force outside the centre of mass.
Centre of Mass ­ The point at which the body is balance in all directions.
Fulcrum ­ The fixed point of rotation about which the leaver moves.
Effort ­ The muscular force applied to create the motion of a lever.
Load ­ The resistance or weight to be moved.
Moment of Force ­ The effectiveness of a force to create rotation about an axis.
Angular Distance ­ The angle through which a body has rotated about an axis in moving from the first
position to the second.
Angular Displacement ­ The shortest change in angular position. It is the smallest angle through which
a body has rotated about an axis in moving from the first position to the second.
Angular Speed ­ The angular distance travelled in a certain time.
Time Taken (Seconds) = Angular Speed (Radians per second)
Angular Velocity ­ The angular displacement travelled in a certain amount of time.
Time Taken (Seconds) = Angular V elocity (Radians per second)
Angular Acceleration ­ The rate of change of angular velocity.
Angular V elocity (Radians per second)
Time Taken (Seconds) = Angular Acceleration (Radians per second2)
Angular Analogue of Newton's Law 1 ­ A rotating body continues to turn about its axis of rotation
with constant angular momentum unless acted upon by an external torque.
Angular Analogue of Newton's Law 2 ­ The rate of change in the angular momentum is directly
proportional to the size of the external torque/ moment of force applied, and in the same direction.
Angular Analogue of Newton's Law 3 ­ For every torque that is exerted by one body on another,
there is an equal and opposite torque exerted by the second body of the first.
Moment of Inertia ­ The resistance of a rotating body to change its state of motion.
Sum of the mass of the body(Kgs)X Distance of the mass from the axis of rotation 2 = M oment of Inertia (Kgm2)
Angular Motion

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Angular motion is probably the most common technique used in sport. It is created by
applying an external force outside the centre of mass (eccentric force), the axis of rotation becomes
where the centre of mass is located.
An example of angular motion is a somersault in gymnastics or high board diving.
Stability
This is the point at which the body is balanced in all directions. It can be manipulated by
changing the distribution of mass or changing the body's shape.…read more

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Dodge ball ­ The performer will want to be able to change their state of motion quickly in
order to dodge the ball.
Gymnastics ­ A gymnast also has to perform a series of tumbles that being unstable will allow
them to change direction quickly and earn a higher mark.
Badminton ­ They need to be able to move around the court quickly to keep up the rally,
therefore being able to change their direction of motion quickly will be advantageous.…read more

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The fulcrum is located between the load and the effort. An example of this is the elbow in an
over arm throw in rounders. The load is the weight of the weight of the arm, hand and the rounders
ball. The fulcrum is the elbow joint. The effort is the muscular force exerted by the Tricep Brachii
pulling on the Ulna (the lever). It is a very stable lever and has lots of control of motion, though they
have a limited range of motion.…read more

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An axis of rotation in an imaginary line about which a body will rotate. The importance of
manipulating the centre of mass returns here. There are 3 axes about which the body can rotate ­
Longitudinal such as a pirouette
Transverse such as a front somersault
Frontal such as a side somersault.
Angular Analogue of Newton's Laws of Motion
First Law ­ A rotating body will continue to turn about its axis of rotation with constant angular
momentum, unless acted upon by an external torque.…read more

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A simple example would be if you were spinning on a chair, opening your arms
and legs out, then tucking them in will help conserve momentum.
Angular momentum is referred to as a conserved quantity. A performer will want to
generate as much as possible at take-off and conserve its quantity throughout a sporting action.
Common sports angular momentum is considered in is diving, gymnastics, ice skating and skiing.…read more

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They will tuck their arms and legs into their body, close to the transverse axis to lower their
moment of inertia which will increase their angular velocity to increase the overall speed of rotation.
This does although give them little control, but it is not needed as they are not in contact with the
ground. Here and angular momentum is conserved.…read more