Assignment Exi Sci End of Term

Biomechanics

Biomechanics is the science of human movement. It is the internal forces produced by muscles and tendons working against the external forces of gravity, wind resistance and friction and the influence they have on human performance.

Mass

The amount of matter of an object.

Weight

The gravitational pull on an object due to it having mass.

Inertia

A body's reluctance to change its state of motion, directly proportional to its mass.

Velocity

Speed in a given direction, calculated as distance divided by time, measured in m/s. V = Distance / time.

Acceleration

A change in velocity divided by time, measured in m/s. a = (final v - initial v) / time.

Momentum

The mass of an object multiplied by velocity, measured in Kg/m/s. M = m x v.

Linear Motion

Motion where a body and all parts connected to it travel the same direction and at the same speed. For example:

A person standing still on an escalator or in a lift. 

Swimmers who push off the wall and streamline through the water.

Curvilinear Motion

Motion where the whole body moves in a curved path. For example

The flight path of a shot putt or long jumper

A snowboarder gliding on a rainbow rail

Angular Motion

Motion where a body and all parts of it travel along a circular path through the same angle and in the same direction. For example:

A gymnast rotating around a high bar

A figure skater spinning on the ice

General Motion

The combination of both linear and angular motion, the most common type of motion. For example:

Running where your legs are rotating to move the body in a linear path

Butterfly where the arms are rotating through the water to propel the body in a linear path

Force

The pushing or pulling activity that tends to alter the state of motion of a body, measured in Newtons (N).

Internal Forces

Forces generated by muscles and tendons in the body.

External Forces

Forces such as friction, gravity, air resistance, and fluid resistance that need to be overcome to move the body.

Moment of Force

The product of the size or magnitude of the force and the distance between the applied force and the axis of rotation, measured in Newton metres (Nm).

Isometric Force

Force without motion; muscles contract without producing motion.

Isotonic Force

A force able to change the state of motion of the object.

Concentric Force

A force applied through the centre of gravity of an object resulting in linear motion.

Eccentric Force

A force applied to an object that is off-centre, resulting in linear and angular motion or just angular motion if the axis is fixed.

Projectile

An object that is automatically under the influence of gravity and air resistance as it travels through the air.

Factors Affecting Projectile Motion

Elements that influence the trajectory and distance of a projectile, including application of force, angle of release, and height of release.

Application of Force

The force applied to the projectile which affects its motion, varying in amount and direction.

Angle of Release

The angle at which a projectile is launched; for maximum distance, the optimal angle is 45º.

Height of Release

The initial height from which a projectile is released; higher release points result in further travel due to increased flight time.

Gravity

A constant force acting on all projectiles, pulling them towards the Earth at a rate of 9.8m/s.

Air Resistance

A force working against the motion of a projectile, reducing its forward speed and creating drag.

Resistive Forces

Forces that oppose the motion of a projectile, including gravity and air resistance.

Summation of Force

The process of achieving maximal force through timing, muscle contraction, and technique.

Simultaneous Force Summation

A method where body parts act together at one instant to generate force, such as in a long jump take-off.

Sequential Force Summation

A method where body parts are moved in a sequence to generate maximum force, such as in a shot put.

Centre of Gravity (C of G)

The point at which all the weight of an object is evenly distributed and about which the object is balanced.

Balance

The ability to maintain equilibrium of the body while stationary or moving.

Stability

The ability to use body structures efficiently in different sport-related positions while maintaining balance.

Optimal Angle of Release

The ideal angle for maximum horizontal distance, which is 45º.

Effects of Air Resistance

Factors such as size of the projectile's surface area, shape, mass, velocity, momentum, and spin that influence air resistance.

Drag Force

The resistance force that acts against the motion of a projectile as it moves through the air.

Frictional Force

A force that acts against the motion of a projectile as it pushes through the atmosphere.

Timing of Each Sequence

The coordination of body parts in a sequence to achieve optimal force generation.

Body Parts with Greatest Mass

The larger body parts, such as legs and hips, that should be used to start the action in force generation.

Smaller Body Parts

The lighter body parts that should be used at the point of release or impact as they move with greater velocity.

Centre of Gravity (C of G)

The point where the mass of any object is equally distributed around, meaning the weight is balanced in all directions.

Hollow Centre

If an object has a hollow centre, then the C of G is in the centre of the hollow.

Uneven Mass Distribution

Some objects in sport have uneven distribution of mass, favoring a particular side, such as a lawn bowl that has more mass on one side to make it curl.

Irregular Shape

The human body is an irregular shape and the C of G may not be in the middle.

Arrangement of Body Parts

The C of G in the human body depends on how the body parts are arranged, specifically the position of the arms and legs relative to the trunk.

Flexibility of the Human Body

The human body is flexible and can assume a variety of positions, causing the C of G within the body to change often.

Repetitive Movements

During repetitive movements like running, the C of G will vary slightly with each bounce and stride performed.

Quick Rotation

In activities that require quick rotation, such as a somersault, the C of G may need to move outside of the body to allow for fast rotation.

Factors Affecting Stability

There are 3 main factors that will affect an athlete's stability: height of C of G, size of the base support, and position of the line of gravity.

Height of Centre of Gravity

The lower the C of G, the more stable the body; a shorter person is therefore more stable than a taller one, all other factors being equal.

Base Support Size

The wider the base of support, the more stable the body; a person with their legs spread apart is more stable than one with their legs together.

Position of the Line of Gravity

When the line of gravity is directly in line with the centre of the base of support, the body is considered to be most stable.

Adjusting the Line of Gravity

In contact sports, athletes need to shift their position of the line of gravity within their base support to prepare for contact.

Newton's First Law of Inertia

An object at rest will tend to remain at rest until acted upon by an outside force; similarly, an object in motion tends to remain in motion unless acted upon by an outside force.

Example of First Law

If a force is applied to a chair, it will move; if not, it stays still.

Newton's Second Law of Acceleration

When a body is acted upon by a force, its resulting change in acceleration is proportional to the force causing it.

Acceleration and Force

The greater the force, the greater the acceleration; for example, a player bunting a ball with a small force results in less distance than with a full swing.

Acceleration and Mass

Acceleration is inversely proportional to mass; greater mass results in smaller acceleration.

Newton's Third Law of Action/Reaction

For every action, there is an equal and opposite reaction.

Example of Third Law

When jumping, you apply a force to the ground and the ground applies the same force back through you.

Rotational Motion in Sports

In rotational motion, two objects involved in action-reaction are often body parts, requiring rotational movements around a joint to create momentum.

Soccer Header Example

During a soccer header, a player jumps and thrusts the upper body forward to head the ball (action), while the lower body responds for balance (reaction).

Moment of Inertia

A body's reluctance to rotate or begin angular motion.

Moment of Inertia Formula

Moment of Inertia = Mass x Moment Arm

Moment Arm

The distance from the axis of rotation to the end of the object.

Effect of Decreasing Moment of Inertia

It can make it easier to handle a body or object but will decrease the amount of force produced.

Effect of Increasing Moment Arm

It makes it harder to handle a body or object but increases the amount of overall force produced.

Diving - Layout

The moment arm is long, moment of inertia is large and rotation is four times slower than in the tuck position.

Diving - Piked

The body mass is further from the axis of rotation, moment arm is longer, and moment of inertia is increased.

Diving - Tucked

The body mass is close to the axis of rotation and moment of inertia is small, resulting in rapid rotation and angular velocity.

Momentum

A body in motion possesses mass and velocity; the product of both is known as momentum.

Momentum Formula

Momentum = mass x velocity

Conservation of Momentum

When two or more bodies collide, the total momentum before impact is the same as after impact.

Momentum Transfer Example

When a bat meets a ball, the total momentum is equal to the momentum of the bat and the momentum of the ball.

Momentum Calculation Example

Mass of bat = 4.0kg, Mass of ball = 0.5kg, Speed of bat before impact = 10m/s, Speed of ball before impact = 100m/s.

Momentum Loss and Gain

Momentum lost by the leg is gained by the ball during a collision.

Newton's Third Law

Momentum can be transferred from one body part to another, as seen in a gymnast's kip movement.

Transfer of Momentum - Airborne

When a body is airborne, total momentum cannot change unless acted upon by an external force.

Example of Momentum Transfer in Diving

As a diver goes into a pike position, momentum is transferred to the legs when the upper body and legs collide.

Tight Body Position

Results in more rotational/angular motion and a small amount of inertia.

Open Body Position

Results in less rotational/angular momentum and a larger amount of inertia.

Coefficient of Restitution

A term used to describe or measure the result of the impact of two objects.

Coefficient of Restitution Calculation Methods

Calculated by the difference between height of rebound and height of release, or the difference between the velocity of approach and the velocity of separation.

Velocity of Separation

Will be less than that of approach because momentum is transferred to the ground.

Coefficient of restitution

A measure of how much momentum is transferred from one object to another during an impact, always less than 1.0.

Factors affecting coefficient of restitution

Elasticity of the two objects, temperatures, frictional forces between the two objects, and the speed of impact.

Elasticity

The ability of a ball to return to its normal shape after impact, affecting its coefficient of restitution.

Optimum impact speed

The ideal speed at which a ball should be hit to maximize performance in hitting sports.

Rolling friction

The type of friction that occurs when a ball rolls over a surface, which is less than sliding friction.

Sliding friction

The frictional force that opposes the sliding motion of an object, equal to the force causing the slide until sliding begins.

Limiting friction

The maximum magnitude of friction that can be exerted before sliding commences.

Inertia

A body's resistance to change its state of motion, greater with increased mass.

Momentum

The product of an object's mass and its velocity.

Impulse

The change in momentum of a body, measured in Newton seconds.

Impulse formula

Impulse = force x time.

Friction

The force that opposes motion whenever one body moves or tends to move across the surface of another.

Factors increasing friction

Use of magnesium powder, waxed skis, lycra suits, and leather soles on wooden floors.

Impulse and accuracy

Techniques that allow longer contact with a ball can provide greater force and increased accuracy.

Compression of the ball

The degree to which a ball is compressed during impact, affecting energy transfer.

Speed of impact

The velocity at which two objects collide, influencing the coefficient of restitution.