# OCR A2 P.E Biomechanics - Linear Motion

Everything you need to know about Linear Motion. Let me know if anything needs editing or adding in. Thank you! Hope it helps

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Biomechanics ­ Linear motion
Glossary
Linear motion ­ Motion in a straight line in the same speed, distance and direction.
Mass ­ A quantity of matter measured in kilograms (Kg).
Inertia ­ The resistance of a body to change its state of motion.
Weight ­ Mass (Kg) X Gravity (Given in exam) = Weight (N)
Momentum ­ Mass (Kg) X Velocity (Meters per second) = Momentum (Kgms-1)
Distance ­ The path taken in moving from the first position to the second. Measured in meters.
Displacement ­ The shortest straight line route between two positions in a stated direction.
Measured in meters.
Speed ­ A body's movement per unit of time with no reference to direction.
Distance (Meters)
Time Taken (Seconds) = Speed (Meters per second)
Velocity ­ The speed of a body in a given direction, and is the rate of change of displacement.
Displacement (Meters)
Time Taken (Seconds)= V elocity (Meters per second)
Acceleration ­ The rate of change at which a body changes its velocity. When increasing, it is known
as positive acceleration, and when it is decreasing (deceleration) it is known as negative acceleration.
Zero acceleration is when the body is either moving at a constant speed or at rest.
Change in velocity (Meters per second)
Time Taken (Seconds) = Acceleration (Meters per second-2)
Or
First velocity-Initial velocity (Meters per second)
Time Taken (Seconds) = Acceleration (Meters per second-2)
Action force ­ The force you apply to an object.
Reaction ­ The force the object applies to you.
Linear Motion
Linear motion in sport is created by applying a force to the centre of mass, which therefore
prevents spin. An example of this would be a sky diver that had reached terminal velocity (constant
speed).
Newton's Laws of Motion

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First Law - Inertia
A body will remain at rest or at a constant speed until an external force is applied.
E.g. A 100M sprinter will remain in the blocks at rest until an force is applied to the blocks.
Second Law ­ Acceleration
The rate of change in momentum is directly proportional to the size of the external force.
E.g. The harder a 100M sprinter pushes off the blocks, the faster they will accelerate.…read more

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A ­ B = A football player would accelerate to chase
an opponent. The football player would then
decelerate as they approach the opponent.
B ­ C = The football player stops to tackle the
opponent to get the ball.
C ­ D = The football player accelerates in the
opposite direction and then decelerate to pass the