Biomechanics

Question 1

Remember to go EDAP with Biomechanical questions worth 3 or 4 marks.

Answer 1

E - Outline the relevant equation

D - Define the relevant concept

A - Apply to the question asked

P - Performance - Link the relevant concept to the impact (positive or negative) on performance. Using data where and when possible.

Question 2

Definitions of Newton’s Three Laws of Motion and be able to describe examples of each in sporting situation

Answer 2

Law of inertia
A body will remain at rest or in uniform motion in a straight line unless acted upon by an external force (For instance, consider a game of soccer (football). When the ball is at rest on the field, it will remain stationary unless a player applies a force to kick it. Once the ball is in motion, it will continue moving in a straight line at a constant speed unless acted upon by another force, such as the friction of the grass, the resistance of the air, or a player’s foot intercepting it.)

Law of acceleration
A force applied to an object will produce a change in motion in the direction of the applied force that is directly proportional to the size of that force. Simply, more increased mass = decreased acceleration. Increased mass = decreased acceleration (In gymnastics, when an athlete performs a vault, the force applied during takeoff determines the acceleration with which they ascend into the air. The more force they apply, the greater their acceleration and the higher they can jump.)

Law of action and reaction
When two objects come into contact with one another, they exert forces that are equal in size but opposite in direction on each other. The law states; for every action there is an equal and opposite reaction (As a swimmer pushes against the water with their arms and legs, the water exerts an equal and opposite reaction force that propels the swimmer forward. This reaction force allows the swimmer to move through the water efficiently.)

Question 3

External forces that act on the body - friction, drag force, gravity

Answer 3

Friction - friction is when two surfaces come in contact with eachother. Friction opposes the motion of an object. To overcome friction, you must increase force

Drag force (air and water resistance) - Drag force oppose the direction of the object slowing it down. It is affected by a number of different factors including: air density, cross sectional area of the body, and the speed the object is traveling. Increase in speed results in increase in drag

Gravitational force - Force of attraction between two bodies or objects. Causes objects to fall downwards. The acceleration due to gravity is equal to 9.8m/s. All objects projected into the air are affected by the force of gravity

Question 4

Inertia

Answer 4

Inertia is the tendency of an object to resist change in its state of motion. The amount of inertia an object is directly related to its mass

Greater mass = greater inertia = greater force needed to change its state

Question 5

Mass

Answer 5

(weight divided by gravity)

Mass is the weight of the individual divided by gravity

Question 6

Momentum

Answer 6

(mass x velocity)

Momentum is the mass of the individual times by the velocity they are moving at

Is a measure of the amount of motion an object has and its resistance to changing that motion

A stationary object has zero momentum as it has zero velocity

If two objects have the same mass then the object with the greater velocity will have greater momentum

Question 7

Conservation of momentum

Answer 7

Conservation of momentum states that the total momentum of the system before the collision is equal to the total momentum after the collision

Question 8

Summation of momentum

Answer 8

Summation of momentum is any movement that requires multiple muscle groups to perform a skill from start to end

Example: hitting a golf ball as far as possible the club head speed must be at its maximum at the point it connects with the ball. This a s result of summation of momentum of the lower body, trunk, hips, arms and wrist

Question 9

impulse

Answer 9

(force x time)

impulse is the amount of force applied times by the amount of time spent

is equal to the change in momentum of an object, can be applied to an object to either increase or decrease the velocity

Question 10

Moment of inertia

Answer 10

The resistance of an object to changes in its angular motion

Question 11

angular momentum

Answer 11

(moment of inertia x angular velocity)

Angular momentum is the total motion of a rotating body, but broken down it’s this: moment of inertia is the resistance to change in its angular motion, and angular velocity is the speed an object is rotating/spinning. So in relation to angular momentum it is, the resistance to change in its angular motion (moment of inertia) times by the speed at which an object is rotating/spinning.

When moment of inertia is increased, angular velocity is decreased, but when moment of interia is decreased, angular velocity is increased.

Question 12

Conservation of angular momentum

Answer 12

States that in the absence of external torques, the angular momentum of a system remains constant (In golf and tennis, players use the conservation of angular momentum when swinging the club or racket. By extending their arms during the swing and then pulling them in closer to their body, they can increase the angular velocity of the swing while conserving angular momentum, allowing for more powerful shots)

Question 13

Difference between linear motion and angular motion

Answer 13

The difference between linear motion and angular motion is that linear motion is motion along a straight line where all parts of the travel: the same distance, in the same direction, in the same time, whereas, angular motion is motion or rotation occurs when an athlete or object rotates around an axis

Question 14

Distance

Answer 14

Distance is the length of the path a body follows

Question 15

Displacement

Answer 15

Displacement is the length of a straight line joining the start and finish points

Question 16

Force

Answer 16

(mass times acceleration)

Force is the mass of the individual times the acceleration at which they are moving at

Question 17

Speed

Answer 17

(distance divided by time)

Speed is the distance the individual travelled divided by the amount of time it took them to cover the distance

Question 18

Velocity

Answer 18

(displacement divided by time)

Velocity is the length of displacement divided by the amount of time spent

Question 19

Acceleration (positive, negative, zero)

Answer 19

(change in velocity divided by change in time)

positive acceleration - if the velocity of an object increases in the direction of the motion

negative acceleration - when its velocity is decreasing.

zero acceleration - when the velocity of the object remains the same throughout

Question 20

Torque

Answer 20

(Force times lever time)

(greater torque = greater angular acceleration)

Question 21

Projectile motion - HEIGHT, ANGLE, SPEED of release (HAS principle)

Answer 21

Height - when the height of release is the same as the landing height then the best angle of release is 45 degrees. When the point of release is higher than the landing point. When the velocity of release and the angle of release remain constant, a projectile released from a higher will travel further as it has a longer flight time.

Angle - is the angle the object is projected into the air and will depend on the sport. Where the release and landing points are at the same level the best angle for maximum horizontal distance is 45 degrees. This gives the best combination of vertical velocity to give optimal flight time and horizontal velocity to give distance

Speed - is the most important factor when trying to maximise the horizontal distance a projectile will travel. The greater the force applied, the greater will be the speed at release and the further the projectile will go

Question 22

What is Stability and what is Balance? How are they related? Use examples

Answer 22

Stability is the resistance to the disruption of equilibrium

Balance is the ability to control equilibrium

Relation - Increased stability = increased balance (wrestlers increasing base of support)

Decreased stability = decreased balance (swimmers on the block minimise so that only a small movement initiates dive)

Question 23

Factors that affect stability - Base of support, Centre of gravity (including line of gravity), Body Mass, Friction.

Answer 23

Base of support - Larger base of support - greater stability. Base of support is the area bound by the outside edges of the body parts in contact with the surface

Centre of gravity - The point at which its weight is balance, regardless of the position of the body. (generally found at the naval). Higher COG results in decreased stability. Lower COG results in increased balance and stability. In sports flex at hips, bending knees and flex ankles result in lowering COG

Body mass - more mass equals more stability

Friction - more friction or stability

Question 24

What is a mechanical advantage?

Answer 24

Force arm divided by resistance arm

This equation essentially states that if the force arm is longer than the resistance arm we will have a

mechanical advantage.

Question 25

Discuss the mechanical advantage of second-class and third-class levers. How are they different?

Answer 25

The mechanical advantage of a class II levers is always more than 1, because the effort arm is always longer than the load arm.

class III levers is always less than 1 because the effort arm is always shorter than the load arm.

Question 26

The impact of changing lever length

Answer 26

The longer the lever arm, the greater the mechanical advantage, and the easier it becomes to lift heavy loads. However, increasing the length of the lever arm also increases the distance over which the input force must be applied, which can make it more difficult to move the lever

Question 27

First, Second and Third class levers. Examples of each class of lever in the human body

Answer 27

First - (RAF) agonist muscle provides the applied force and the antagonist muscle provides the resistance. First class levers can be manipulated to increase the force output by increasing distance of the force arm or the speed and ROM of the lever

(the joint formed by the top of the vertebral column and skull)

Second - (ARF)

very few examples in the human body.

resistance is closer to the axis than the force. Therefore the force arm is longer than the resistance arm. Beneficial in increasing force output and useful when heavier loads need to be moved

Eg person standing on their tiptoes. The

resistance to be moved is the weight of the

body, the axis is the toes and the force is

the tension generated in calf.

Third - (AFR) most common in both the body and in sporting applications. resistance is generally at the end of the lever. In third class the resistance is further from the axis than the force being applied. Requires greater force to move resistance but greater ROM and speed are gained