Biomechanics in Sport
Newtons Laws
Newton's First Law refers to inertia and that an object in motion or at rest will stay in its current state unless acted upon by an outside force.
Newton's Second Law is force equals mass times acceleration
Newton's Third Law states that for every reaction there is an equal and opposite reaction.
Newton's Second Law is force equals mass times acceleration
Newton's Third Law states that for every reaction there is an equal and opposite reaction.
Forces in Sport
Isometric
A force that does not cause a change in motion. For example when muscles are tensed to hold something tight like a tennis racquet. |
Isotonic
Isotonic force causes a change in motion. Hitting a tennis ball with a racquet causes a change in motion. Catching a basketball is another example as the force involved in catching the ball causes it to stop. |
Sub-maximal
Sub-maximal force is restricted or limited effort. For example putting a golf ball requires sub-maximal force. |
Maximal
Maximal force is when you apply as much effort as possible goes into applying a force. Full muscle contraction occurs. Maximal force can be achieved simultaneously. All body parts contract at the same time to produce a force. It can also be achieved when different parts move in sequence to produce a specific force. For example driving a golf ball. |
Inertia
Inertia is a body’s total resistance to changing its state of motion. The heavier the item, the greater the force is needed to move it or stop it, therefore the greater its inertia.
Force reception
Force reception refers to absorbing the momentum of a moving item. In soccer when a ball is being kicked to another player, the force of the ball will need to be absorbed by the foot of the player receiving the pass.
Levers
First class- In the case of a first class lever the fulcrum is in between the force arm and resistance arm. For example the oars in rowing are first class levers.
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Second class- In a second class lever the resistance load is in the middle between the fulcrum and force arm. A wheelbarrow is a second class lever.
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Third class- All limbs on the body are third class levers. It is the most common type of lever used in sport. For example the fulcrum could be the shoulder joint. The resistance force is a ball and the force arm are all the muscles. The resistance force is at one end, the fulcrum at the other end and the force arm in the middle.
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Types of movement
Linear- considered normal motion. Linear motion occurs when all components of an object or body travel at the same speed at the same time. Ski jumper coming off a ramp and gliding through air is an example of linear motion. A ball travelling through air is another example of linear motion.
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Angular- the weight of an object or body rotates around an axis during travelling In relation to the third class lever. During motion the parts that are further from the point of axis or fulcrum move a greater distance in the same amount of time going faster. In relation to the body it means travelling around the medial, horizontal or vertical axis. When ice skaters turn they turn around the vertical axis. Divers spin around around a horizontal axis as the dive. Gymnasts cartwheel around a medial axis. The moment of resistance when an object begins angular motion is called the moment of inertia.
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General- when both linear and angular types of motion are present at the same time. It is the most common type of motion in sport. Running, tennis, cycling, rowing and kayaking are all examples of general motion.
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Projectiles
In theory, the optimal angle of release for a projectile is 45 degrees. This is because it provides equal amounts of vertical and horizontal force.Five factors that can influence the angle of release of a projectile:
- Speed
- Height
- Gravity
- Air resistance
- Spin
Friction in football
In football players use increased and decreased friction to their advantage. Friction is caused when two surfaces make contact with each other.
The grass on soccer pitches is kept at a certain length to make sure that the friction remains constant. The shorter the grass the faster the ball will travel because there is less friction. Likewise the longer the grass, the slower the ball will travel because of the increased friction. Players use the friction to
judge how much force is needed to pass the ball and how it will move along the pitch. Players when attempting to slide tackle find it easier when there is less
friction, such as on a wet pitch. Players are less likely to hurt themselves by friction burn on the pitch if there is less friction. But they have less control over their tackles when there is less friction so they may inure other players.
Football players wear football boots with studs so that they can increase the friction between them and the pitch so that they can make sharp turns easier and are less likely to slip. Cleats have greater friction than runners. Players only require moulded plastic studs on pitches that are dry because they have more friction. Wet pitches have less friction and players often opt for metal studs which increase friction.
Friction applies so balls used in soccer as well. If a soccer ball is too gripy and has too much friction between it and the player's boot, the ball will get caught up in the player's feet. If the ball is too slippery or smooth and doesn’t have enough friction between the player’s boots, the softest of touches will force the ball to move further than the player predicts. Footballers use friction in the air to create spin on the ball and make it dip and curve in the air. Players use friction so that the ball can catch in the air and change its path of motion. Friction makes the ball slow down.
The grass on soccer pitches is kept at a certain length to make sure that the friction remains constant. The shorter the grass the faster the ball will travel because there is less friction. Likewise the longer the grass, the slower the ball will travel because of the increased friction. Players use the friction to
judge how much force is needed to pass the ball and how it will move along the pitch. Players when attempting to slide tackle find it easier when there is less
friction, such as on a wet pitch. Players are less likely to hurt themselves by friction burn on the pitch if there is less friction. But they have less control over their tackles when there is less friction so they may inure other players.
Football players wear football boots with studs so that they can increase the friction between them and the pitch so that they can make sharp turns easier and are less likely to slip. Cleats have greater friction than runners. Players only require moulded plastic studs on pitches that are dry because they have more friction. Wet pitches have less friction and players often opt for metal studs which increase friction.
Friction applies so balls used in soccer as well. If a soccer ball is too gripy and has too much friction between it and the player's boot, the ball will get caught up in the player's feet. If the ball is too slippery or smooth and doesn’t have enough friction between the player’s boots, the softest of touches will force the ball to move further than the player predicts. Footballers use friction in the air to create spin on the ball and make it dip and curve in the air. Players use friction so that the ball can catch in the air and change its path of motion. Friction makes the ball slow down.