Biomechanical
Principles of Force and
Momentum
Newton’s Three Laws of
Motion
O Newton has 3 Law’s of motion, these are:
O 1. The Law of Inertia
O An object will remain at rest or in a uniform motion
in a straight line unless acted upon by an
unbalanced force.
O 2. The Law of Force, Mass & Acceleration
O F=MxA
O The acceleration of an object depends on the mass
and force of an object.
O 3. The Law of Action & Reaction
O For every action there is an equal and opposite
reaction.
Biomechanical Principles of Force
O Force is a push or pull on an object upon interaction with
another object
O Two important points to be aware of
The point of application of the Force (where the force is applied)
O The line of action of the Force
O
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
O
Force is calculated by
F = ma
O
O
(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
O Contact Forces:
O Applied force
O Gravitational force
O Normal force
O Frictional force
O Air resistance force
O Tension force
O Spring force
O Action at distance forces:
O Gravitational
O Electrical
O 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
O
http://www.youtube.com/watch?v=fqQVpQ0AeAc
Ground vs Mass
O http://www.youtube.com/watch?v=eiYMK7wf57g
O
Biomechanical Principle of
Momentum
O
Momentum is the product of the mass and the velocity of an object.
O
O
O
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
O
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
O Momentum = mass x acceleration
O When an object has momentum it is in motion. There
are two types of motion:
O Linear motion: movement in a particular direction.
O Rotational motion: movement about an axis.
O Physics of Football – Momentum
O https://www.youtube.com/watch?v=hTZI-kpppuw
Biomechanical Principle of
Momentum
Velocity affects momentum.
Examples of this are
O 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
1.
2.
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
O 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
O
O
1.
2.
3.
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=iThOfiT1to
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
O Newton’s 3 laws of motion are a critical component of
O
O
O
O
biomechanics. These are:
O 1. The Law of Inertia
O 2. The Law of Force, Mass & Acceleration
O 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