Unit 2 PE Biomechanics

What is Newton’s first law of motion?

• The Law of Inertia

A body will remain at rest or in a uniform motion unless acted upon by an external force.

What is Newton’s second law of motion?

• The law of acceleration

• Equation: F=ma

Force applied to an object will produce a change in motion (acceleration) in the direction of the force, that is directly proportional to the size of the force and inversely proportional to its mass.

What is Newton’s third law of motion?

• Law of action/reaction

For every action there is an equal and opposite reaction

How do you answer almost all biomechanics questions?

Go DEEP

1. Define EG Law of Acceleration states…

2. Equation EG F = ma

3. Explanation EG The cyclist with the smaller mass will accelerate faster

4. Performance link EG Thus they will overtake and win the race

How do you define momentum? What does it describe?

Definition: The amount of motion an object has and its resistance to changing that motion

Formula: Momemtum = mass x velocity

• Measured in kg/m/s

• Objects with greater mass have greater momentum and therefore require larger force to stop

• Hence many sports players gain an advantage by increasing mass as long as it’s not at the expense of their velocity

What is conservation of momentum? What does it apply to?

Definiton: The transfer of momentum from one body to another

• Applies to any collison between two objects EG foot on ball, two players, foot and ground

• Total momentum prior to impact is equal to total momentum after impact (ignoring a small amount lost in collision)

How do you define force summation/summation of momentum?

Force summation: The correct timing and sequence of body segments to produce maximal force

EG When trying to throw, kick, hit an object as far as possible

• Momentum = mass x velocity

• Use BEST (Body parts, SEquence, Stability, Timing) to produce maximum force

How can maximum force summation/summation of momemtum be achieved?

1. Body parts: Use an many body parts as possible

2. SEquence: Move the heavier and slower (M=mxv) body parts first (legs, trunk) followed by the lighter and faster body parts (arms, wrists and fingers)

3. Stabilisation: Body parts must stabilise once they pass momentum to ensure momentum is not lost

4. Timing: Move the next body part only once the previous body part has reached maximum velocity

• Follow through with the movement

How do you define impulse? How can it occur?

Definition: The change in momentum of a body

Equation: Force x Time

• Occurs in 2 ways: Speeding up (when force acts in the same direction as motion) and slowing down (when force acts opposite to the motion)

What is force reception? How does this affect impulse?

Definition: The process of stopping the momentum of a projectile and bringing it’s momentum to zero

• The projectile will be stopped regardless of it’s initial momentum

• Therefore the change in momentum is fixed, so the impulse is constant

• Since Impulse = Force × Time, force and time have an inverse relationship

• Therefore, increasing the time over which force is applied decreases the force required to stop the projectile

If momentum is velocity x mass, and impulse is force x time, what are the defintions of mass, force and velocity?

Force: A push or a pull

Mass: The amount of matter that makes

Velocity: The rate of change in position (displacement) over time