Biomechanics & MLC

Define momentum.

A measure of the amount of motion possessed by a moving body. It is the product of mass and velocity.

Define impulse.

The application of force over a period of time to change the momentum of an object. Impulse = force × time.

Describe how an impulse can increase momentum.

An impulse can create momentum by increasing the momentum of an object from zero, or increase the momentum of a moving object.

Describe how an impulse can decrease momentum.

An impulse can decrease the momentum of a moving object and can eventually take its momentum back to zero.

Explain how impulse is applied in sporting contexts.

In cricket, a player can use “soft” hands when catching a ball to slowly reduce its momentum by increasing the time taken to absorb the force. In shot put, a shuffle throw increases both the time of force application and usually the magnitude of force, leading to a greater impulse and therefore a greater change in momentum.

Define coefficient of restitution.

Coefficient of restitution measures the elasticity of the collision between an object and a given surface. It measures how much energy remains in the object after a collision occurs. COR is measured from 0 to 1, where 1 is a perfectly elastic collision and 0 is a perfectly inelastic collision.

What effect do equipment and surfaces have on coefficient of restitution?

Different equipment and surfaces have different CORs. A new tennis ball has a higher COR than an old tennis ball, and clay/hard courts have a higher COR than grass courts.

What effect does temperature have on coefficient of restitution?

Increasing the temperature of a ball increases its COR. A warm squash ball is more “bouncy” than a cold squash ball.

What effect does velocity have on coefficient of restitution?

Increasing velocity increases the likelihood of the ball losing energy due to greater compression, resulting in a decreased COR.

Apply coefficient of restitution to a sporting context.

A coach working with junior athletes can use equipment with a low COR because it reduces injury risk and makes it easier for children to develop technique. For example, a tennis ball with a low COR will bounce lower and travel at a slower velocity, making it easier for a junior player to hit.

Define moment of inertia.

The resistance of a rotating object to change its state of motion.

Define angular velocity.

The rate of change in angular position of a body.

Define angular momentum.

The quantity of angular motion possessed by a rotating body.

Describe how moment of inertia changes as body position changes.

If the mass of an object is distributed close to the axis of rotation, the moment of inertia is small and it is easier to rotate the object. As mass moves further away from the axis of rotation, the moment of inertia increases and rotation becomes harder.

Explain how the distribution of mass affects moment of inertia.

Mass distributed away from the axis of rotation increases moment of inertia and makes the object more difficult to control or rotate. Mass distributed close to the axis decreases moment of inertia and makes the object easier to control or rotate.

Explain how moment of inertia can be changed and the benefits of doing so.

Moment of inertia can be changed by moving mass closer to or further away from the axis of rotation. Moving mass closer to the axis decreases moment of inertia, making rotation easier and allowing greater angular velocity. Moving mass further away increases moment of inertia, making rotation harder.

Explain conservation of angular momentum.

Angular momentum can be conserved when there are no significant external torques acting on a rotating body. A decrease in moment of inertia is met with a corresponding increase in angular velocity, and vice versa, so angular momentum remains constant.

Explain how angular momentum can be increased.

Angular momentum can be increased by increasing linear momentum through run-up speed, applying a greater force to the ground or wall at take-off, and improving segmental interaction at take-off.

Define a third-class lever.

A third-class lever has the axis located at one end, the application of force in the middle and resistance applied at the opposite end. It is the most common type of lever in the human body.

Identify the components of a third-class lever in the human body.

The muscle attachment represents the force, the joint usually represents the axis and the weight represents the resistance.

Draw/describe a third-class lever.

Axis — Force — Resistance (A — F — R). The axis is located at one end, force is applied in the middle and resistance is at the opposite end.

Explain why third-class levers are speed multipliers.

Third-class levers are speed multipliers because the end of the lever travels a greater displacement over the same period of time, resulting in the greatest velocity at the distal end.

Give sporting examples of third-class levers as speed multipliers.

Golf clubs, baseball bats and tennis racquets. Increasing lever length can generate greater velocity/angular momentum and transfer greater momentum onto the ball.

Define laminar flow.

Laminar flow is fluid moving smoothly in individual layers or streams.

Define turbulent flow.

Turbulent flow is flow in which the velocity at any point varies erratically.

Outline the impact of laminar and turbulent flow in sport.

Laminar flow is smooth and organised, while turbulent flow is less organised and largely random.

Define pressure/form drag.

Pressure/form drag is the resistance created by the pressure differential between the front and back of an object moving through a fluid.

Define surface drag.

Surface drag is the friction produced between the fluid and the surface of a moving object.

Define wave drag.

The provided PowerPoint material does not provide a definition of wave drag.

Apply pressure/form drag to a sporting context.

An athlete moving forward creates high pressure in front and low pressure behind, producing drag. Cross-sectional area, velocity, surface roughness and shape affect form drag.

Apply surface drag to sporting contexts.

In swimming, water creates surface drag against the swimmer. In cycling, air resistance acts against the cyclist. In skiing/snowboarding, friction between the skis and snow creates drag.

Apply wave drag to a sporting context.

Swimmers create waves at the surface of the water; larger waves result in greater wave drag. Rowing/kayaking boats also create waves at the front and sides.

Define Bernoulli’s principle.

Bernoulli’s principle states that as fluid velocity increases, pressure decreases. Fast-flowing fluid has low pressure, while slow-flowing fluid has high pressure.

Explain how the shape of an object relates to Bernoulli’s principle.

The shape of an object can cause fluid to move at different speeds around it. Higher fluid velocity results in lower pressure and lower fluid velocity results in higher pressure, creating a pressure differential between opposite sides of the object.

Define the Magnus effect.

The Magnus effect describes the effect of rotation on an object’s path as it moves through a fluid. A rotating ball interacts with the oncoming air, resulting in a curve in its flight path.

Analyse the effect of topspin on an object's flight path/bounce.

Topspin causes the ball to drop/dip and travel shorter in flight.

Analyse the effect of backspin on an object's flight path/bounce.

Backspin causes the ball to rise higher and travel further.

Analyse the effect of sidespin on an object's flight path/bounce.

Sidespin causes the ball to curve left or right depending on which side of the ball the spin is imparted.

Define balance.

Balance is the ability to maintain stability.

Identify the factors that affect balance.

Balance is affected by the size of the base of support, height of centre of gravity, position of line of gravity and mass.

Apply balance to a sporting context.

A greater base of support, lower centre of gravity, line of gravity closer to the middle of the base of support and greater mass increase balance.

Define summation of force.

Summation of force is the combination of forces produced by different parts of the body to meet the demands of the task.

Differentiate between simultaneous and sequential/segmental summation of force.

Sequential summation involves different parts of the body producing forces sequentially to maximise force and is generally used for whole-body actions such as throwing, kicking and striking. Simultaneous summation involves body parts moving at the same time and is generally used to produce accuracy.

Apply summation of force to sporting contexts.

Sequential summation is used for actions such as throwing, kicking and striking to maximise force. Simultaneous summation is used to produce accuracy, such as in a netball goal shot.

Define optimal projection.

The provided PowerPoint material does not provide a definition of optimal projection.

Identify factors that affect optimal projection.

The provided PowerPoint material does not provide sufficient information about factors affecting optimal projection.

Apply optimal projection to a sporting context.

The provided PowerPoint material does not provide sufficient information to construct this answer strictly from the PowerPoint.

Define transfer of learning.

Transfer of learning is the influence past experiences have on the learning/performance of a new experience/skill.

Describe skill-to-skill transfer.

A skill previously developed in one sport influences learning a skill in another sport.

Describe theory-to-practice transfer.

The transfer of theoretical skills into practice or performance scenarios.

Describe training-to-competition transfer.

The transfer of skills developed at training into a competition situation.

Explain positive transfer.

A skill gained in one sport helps, benefits or assists performance of a skill in another sport.

Explain negative transfer.

A skill developed in one sport inhibits or hinders performance of a skill in another sport.

Explain zero transfer.

A skill developed in one sport has no impact on learning a new skill.

Describe the preparation phase of the Knudson-Morrison model.

Develop prerequisite knowledge about the skill, gather relevant knowledge about the activity and performer, and select an observational strategy.

Describe the observation phase of the Knudson-Morrison model.

Systematically gather information about the performance or movement.

Describe the evaluation phase of the Knudson-Morrison model.

Identify strengths and weaknesses, prioritise them and identify methods to improve performance.

Describe the intervention phase of the Knudson-Morrison model.

Provide feedback, instruction and practice strategies based on weaknesses identified during evaluation.

Describe the re-observation phase of the Knudson-Morrison model.

Observe the performer in a similar context to the initial observation to determine whether the changes improved performance.

Describe shaping.

Shaping involves learning a simplified or incomplete version of a skill and adding the missing parts as the skill develops. It is suitable for complex skills which have simultaneous elements.

Apply shaping to improve a sporting skill.

A coach can simplify a complex skill and gradually add missing components, such as progressing from running over cones to low hurdles and then competition-height hurdles.

Describe chaining.

Chaining involves breaking a skill down into its component parts and then sequentially learning each component part one at a time. It is suitable for teaching skills which have sequential parts.

Apply chaining to improve a sporting skill.

A skill can be broken into components and learned sequentially, such as teaching the hop, then step, then jump and finally run-up in the triple jump.

Describe static-dynamic training.

Static-to-dynamic involves the player starting with drills involving limited movement and progressing to drills involving movement and additional tasks. Static skills involve limited movement in a predictable environment with limited cues, while dynamic skills involve movement in a less predictable environment with increased cues and decision-making.

Apply static-dynamic training to improve a sporting skill.

Begin with limited movement in a predictable environment so the performer can concentrate on technique, then progress to movement and additional tasks in a less predictable environment.

Discuss authoritarian/autocratic leadership.

The coach makes all decisions. It is useful for inexperienced athletes, emergencies, safety concerns and situations requiring immediate direction.

Discuss democratic leadership.

The coach involves players in decision-making. It is useful for experienced or intrinsically motivated athletes and situations where there is time for discussion.

Discuss laissez-faire leadership.

The coach makes few decisions and allows players to take ownership. It is useful for experienced and intrinsically motivated athletes.

Identify advantages and disadvantages of authoritarian/autocratic leadership.

Advantages: Quick decisions, clear direction, effective in emergencies/high-pressure situations and useful with inexperienced athletes. Disadvantages: Little athlete input, can reduce motivation/enjoyment, creates dependence on the coach and can cause resentment or poor relationships.

Identify advantages and disadvantages of democratic leadership.

Advantages: Increases motivation/commitment, communication and teamwork, builds confidence/leadership and creates a positive team culture. Disadvantages: Decisions can be slow, difficult with large groups, disagreements can occur and it is less effective when quick decisions are needed.

Identify advantages and disadvantages of laissez-faire leadership.

Advantages: Independence/creativity, responsibility/problem-solving, effective with experienced athletes and develops confidence/ownership. Disadvantages: Lack of direction, confusion, performance may suffer, unclear goals/expectations and the coach may appear uninvolved.

Describe video analysis as a method for correction and improvement.

Video analysis provides visual feedback; performance can be replayed, slowed down and compared with an exemplar or previous performance.

Describe checklists as a method for correction and improvement.

Checklists are a performance record against predetermined criteria that provides written feedback.

Describe peer/mentor/coach feedback as a method for correction and improvement.

Peer, mentor and coach feedback provides feedback to the performer.

Describe questionnaires as a method for correction and improvement.

Questionnaires are a method used for learning and skill development in relation to correction and improvement.