Biomechanical Principles of Force and Momentum

Newton’s Three Laws of Motion Newton has 3 Law’s of motion, these are: 1. The Law of Inertia An object will remain at rest or in a uniform motion in a straight line unless acted upon by an unbalanced force. 2. The Law of Force, Mass & Acceleration F = M x A The acceleration of an object depends on the mass and force of an object. 3. The Law of Action & Reaction For every action there is an equal and opposite reaction. Sir Isaac Newton created the 3 laws of motion which include: The law of inertia, the law of force, mass & acceleration, and the law of action & reaction. ***Break down each law with a brief explanation from slides***

Biomechanical Principles of Force Force is a push or pull on an object upon interaction with another object Two important points to be aware of The point of application of the Force (where the force is applied) The line of action of the Force Picture taken from; http://www.wikihow.com/Stop-on-Ice-Skates Reference Montana State University.(1998), http://btc.montana.edu/olympics/physbio/glossary/g06.html The Physics classroom.(2014). http://www.physicsclassroom.com/class/newtlaws/u2l2a.cfm

Biomechanical Principle of Force Force is calculated by F = ma (F = Force, m = Mass, a = Acceleration) Force is reported in the unit called Newtons (SI units) To describe results as Newton we say “10.0 N” is 10 newtons of force Pic Taken from Dharma Consulting ; http://dharmaconsulting.com/products/accelerating-change/

Types of Force Contact Forces: Action at distance forces: Applied force Gravitational force Normal force Frictional force Air resistance force Tension force Spring force Action at distance forces: Gravitational Electrical Magnetic The Physics classroom.(2014). http://www.physicsclassroom.com/class/newtlaws/u2l2a.cfm

Biomechanical Principles of Force Classroom Activity 1. Each student go up to a wall specified by the teacher and try and push it down. Explain why you could or couldn’t move that wall 2. Pair up with someone your own size, stand back to back and try and move the other person back. Try this same concept with someone who is bigger and smaller than you Examples of Force http://www.youtube.com/watch?v=fqQVpQ0AeAc Ground vs Mass http://www.youtube.com/watch?v=eiYMK7wf57g

Biomechanical Principle of Momentum Momentum is the product of the mass and the velocity of an object. Easy description of momentum “how strong a moving object is” The lighter the object the less momentum they will have when moving. Eg : a small pebble or rock The heavier the object the more momentum this will have when moving ; Eg : Train or Car Momentum is calculated by the mass of the body multiplied by its velocity. (Measured in kilogram metres per second.) momentum = mass X velocity(speed) Pic taken from http://www.mikanet.com/museum/item.php?cat=2&index=53 Ref ; Chapter 3—Applying biomechanics to sport pg75 Retrieved 7th March, 2014 from https://www.oup.com.au/titles/secondary/health__and__physical_education/physical_education/queensland/9780195573862/03_RUS_QSPE_3pp.pdf. Physics for kids.(2014). Retrieved March 7, 2014 from http://scienceforkids.kidipede.com/physics/space/momentum.htm

Momentum Momentum = mass x acceleration When an object has momentum it is in motion. There are two types of motion: Linear motion: movement in a particular direction. Rotational motion: movement about an axis. Physics of Football – Momentum https://www.youtube.com/watch?v=hTZI-kpppuw Linear motion – for example: a sprinter accelerating down the track. Rotational motion – the force does not act through the center of mass, but is rather “off-center”, and this results in rotation. For example: ice-skater’s spin.

Biomechanical Principle of Momentum Velocity affects momentum. Examples of this are A batter, either in cricket or baseball trying to hit the ball further will swing the bat quicker, increasing the velocity to apply more momentum Pic taken from http://www.wallpapergate.com/wallpaper10227.html Pic taken from http://news.xinhuanet.com/english/2008-08/20/content_9554767.htm In most sports, mass is constant, so velocity becomes the main factor influencing momentum.

Biomechanical Principle of Momentum Example of mass effecting momentum Chances of stopping a baseball. Its fast but because of its weight you have a chance to stop it, whereas if a car was coming at you, because of the weight which would increase the momentum this would be impossible to stop Momentum can also be used to increase the execution of skills in sports. Example of this is the difference between kicking on the run and kicking off one step Kicking on the run (AFL) ; http://www.youtube.com/watch?v=GPW2ywB7EGk Short Pass (Soccer) ; http://www.youtube.com/watch?v=iThOfiT-1to One step kick (AFL) ; http://m.youtube.com/watch?v=4AwCi1mIv6M

Biomechanical Principle of Momentum Transfer of momentum “Newton’s first law of motion explains that once a body is in motion, it will tend to stay in motion unless acted on by another force. The principle of the transfer of momentum states that momentum cannot be lost—it is just transferred from one object to another.” (Applied Biomechanics of Sport, pg 91) This is simply transferring the weight from one object to another Eg ; The run up gathers the momentum to increase the distance covered in the triple jump or long jump

Biomechanical Principle of Momentum Classroom Activity Look at the difference in distance between a standing jump off two feet and a jump coming off a run of 5+ steps. Do this in pairs or if location is appropriate Ref ; Chapter 3—Applying biomechanics to sport pg91 Retrieved 7th March, 2014 from https://www.oup.com.au/titles/secondary/health__and__physical_education/physical_education/queensland/9780195573862/03_RUS_QSPE_3pp.pdf. Activity 2 Refer to Appendix A : Momentum of the Human Body. Read and complete task in groups of 4-5 Ref : Corrie,M.,Malpeli,R.,Seery,P.,Whittle,R.(2010). Biomechanical Principles of force production. Phyiscal Education VCE unit 1 & 2 1st ed. Nelson Cenage Learning. Pg 105

Conclusion Newton’s 3 laws of motion are a critical component of biomechanics. These are: 1. The Law of Inertia 2. The Law of Force, Mass & Acceleration 3. The Law of Action & Reaction Force = mass x acceleration Types of force: Applied force, Gravitational force, Normal force, Frictional force, Air resistance force, Tension force, Spring force. Momentum = mass x acceleration Two types of motion: linear & rotational