Practical ideas for biomechanics
Biomechanics
topic
Velocity,
Acceleration,
distance,
displacement
Practical Activity
Link to theory
100m sprint with 10m split times
Newtons Laws –
1st, 2nd and 3rd
Demonstrate using cricket bat and tennis
ball, light medicine ball and heavy
medicine ball.
Compare average speed/ velocity,
positive acceleration, negative
acceleration of class versus Usain
Bolts 10m splits during his world
record.
Draw and read displacement/time,
displacement/velocity and
displacement/ acceleration graphs
All 3 Laws are relevant to almost
every sporting situation.
Heavy ball has more inertia, takes
more force to move at same
acceleration due to increased mass
OR same force, smaller ball (mass)
leads to greater acceleration. Bat
applies force to ball and ball applies
equal and opposite force on bat
Or
Do a burpee and ask students to apply all
3 laws.
Or
Throw a tennis ball to each other and
apply all 3 laws then throw a medicine ball
to each other and explain what has
changed with regards to inertia, force,
acceleration
Momentum
Choose the smallest student and the
largest student. Ask the largest student to
take a run up and knock the smallest
student off balance whilst stationary (NOT
REALLY, just pretend). What would
happen if the smaller person ran at the
large person at the same velocity? How
could the small person knock over the
large one?
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Momentum = Mass X Velocity and in a
collision, momentum is conserved so
try and work out which way a collision
will travel depending on different
velocities and masses of items
Or
Use different weighted medicine balls and
throw them so they collide mid-air and
watch what happens
Impulse
(decreased
momentum)
Impulse
(increased
momentum)
Force
summation
or
summation of
momentum
Dropping a basketball with a tennis ball on
top of it shows momentum really well.
Watch the tennis ball fly, and then add in
a 2md and 3rd ball on top of the
basketball.
Egg throw or water balloon activity where
students throw to each other starting
close and gradually moving out until
balloon or egg breaks or they lose their
nerve.
Jump from a chair with bent knees (motor
bikes) then straight knees. How is your
back?
Tee ball with baseball bat. Students can
experiment with how to increase the
distance hit. Start with bunting all the way
through to run up and hit like Happy
Gilmore.
Complete in small groups a throw of a
tennis ball or table tennis ball if you want
smaller throws or need to do it indoors.
Start seated with wrist only, then elbow/
wrist, shoulder/elbow/wrist,
trunk/shoulder/elbow/wrist, move to
kneeling front on hips/trunk etc., side on
kneeling, standing no step, standing step
then run up. Each throw should get
longer. Which body part makes the
biggest difference?
An impulse is a change in momentum
or Force X time. These activities
require a decrease in momentum to
zero. Impulse is constant but by
increasing the time we receive the
force we can decrease the force.
Increasing momentum to maximum
requires the largest force applied to a
ball for the longest time possible. Only
achievable by summating forces and
following through with the shot
Force summation requires using as
many body parts as possible in correct
sequence (largest mass, slowest
velocity (M*v) to smallest mass,
highest velocity (m*V) and timing
(move next body part once previous
part reaches max velocity). Stability is
also important so momentum is not
lost.
Returning ball to wicket keeper form slips
compared to from the boundary- what
changes in terms of force summation
principles
Force
summation
Video people throwing left and righthanded on Hudl. Have competitions to see
who can throw the furthest with both
hands. Hudl can show both footages
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QMA - Try to analyse exactly why
people are not achieving the same
distance on non-preferred hand.
Usually, this is to do with sequence
HUDL demo
simultaneously and you can add angles
Included in
and lines
there but not
left v right handtwo serve
comparison
Torque
I use a phone on a desk to demonstrate. I
push it through its COG, then just off it
and then on its very outside
Or
take soccer penalty shots and experiment
with kicking the ball through its COG,
outside of both sides to see the impact.
Or
Can also use a door to demonstrate. Try
opening the door (pushing) from the
handle and then use the same force to try
and open it near the hinges (pushing).
Same force applied but different moment
arm and thus very different torque
Angular
momentum
and timing (coordination) as well as
instability through the core
Torque = force X moment arm so any
force applied off centre (eccentric)
will cause a torque, but more force
applied further from the centre
(larger moment arm) will cause
greater torque or turning effect.
Kick to kick footy- snap kicks v drop puntsWhat’s the difference?
● Tee ball with baseball bat, plastic
Angular momentum = Moment of
baseball bat or badminton racket.
Inertia (Mass X radius2) X Angular
Students can experiment with
Velocity.
which one hits furthest.
● A batter wants maximum AM
Or
so maximises both MOI and
● 7 stage abdominal test which is
AV. Too small a MOI like the
also helpful for Unit 4. This test
badminton racket and batter
begins with stage 1 the easiest test
cant produce enough
and stage 7 hardest. Essentially
momentum to hit far. What
each stage increases either the
happens if bat is too long or
radius or the mass (MOI) meaning
heavy though?
to maintain same AV requires
● The 7 stage is great to explain
more force or same force applied
that radius is measured from
leads to slower sit up.
the axis to the COG of the
Or
lever or how far mass is
● Running races in pairs where 1
distributed from the axis.
student runs with bent leg
● This shows that unless we
recovery. Stride (normal running)
bend the knees in the recovery
and the other with straight leg only
stride our cadence is too slow
recovery stride.
to run or it takes too long and
we can’t run fast compared to
the bent leg recovery stride.
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Why? MOI is high and AV is
slow
Conservation of
angular
momentum
Levers
Projectile
motion
Projectile
motion
Sit a student on a swivel chair and spin
them around as fast as possible. Ask them
to put their arms and legs out and in to
increase and decrease MOI and observe
the effect on angular velocity or how fast
the chair spins. Add a weight in each hand
and observe the effect being pronounced
when they increase and decrease radius
This is NOT pure conservation of
momentum as that only occurs whilst
airborne but its close.
AM = MOI X AV
So if AM is constant (it’s not in this
example but close enough) then any
increase in MOI (i.e. increase radius
by putting arms and legs out) is met
by a decrease in AV and vice versa.
The weight pronounces the effect on
AV as an increased mass and radius
increases MOI by more!
Dog thrower activity. Buy a class set of dog The arm in a throw is a 3rd class lever
throwers and experiment with how far
built for speed as it has a long
students can throw without one and using resistance arm compared to force
one. Why is it so effective in throwing
arm. The dog thrower extends the
further with less effort?
resistance arm considerably making
Students who are catching can be
the levers mechanical advantage even
reminded of impulse also (soft hands)
less than 1 and far more in favour of
Or
speed. So for the same force applied a
Sit ups to explain how a lever can change
longer lever will develop more speed
rd
nd
from 3 class going up to 2 class going
at its end point thus hurling the ball
down
faster and further.
Or
Try lateral raises/ dumbbell fly’s with
straight arms and then bent elbows.
Which one is easier? Why?
Play a game of basketball, volleyball or
Projectile motion explanations must
tennis. All of these games involve a
include reference to all 3 variables of
projectile that continually needs to be
Height of release, speed of release
released from a different height, at
and angle of release.
differing speeds and angles depending on Why is the spike a more attacking
court positioning. Think of the difference
shot than a dig?
between a lob and a smash or a dig, set
Higher HOR means the AOR can be
and spike.
lower and still get the ball over the
net. If player is close to the net then
they can have a very fast VOR making
the spike hard to return
Quiots and Hookey
Have a set of quiots and hookey in
your classrooms. You can use these
for projectile motion and have
students alter the distance from the
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Balance
Choose the smallest student and the
largest student. Ask the largest student to
take a run up and knock the smallest
student off balance (NOT REALLY. Just
pretend). Observe what the smaller
student does in order to brace for the
impact naturally. What if the smaller
student stood on one foot?
Or
Crouched start for a 50m sprint- race 2
students off but have one lean back in the
crouch start position and one lean
forward. Observe the difference in starts.
Why did the one leaning forward get a
much faster start?
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spike or board and discuss how it
affects HOR, AOR and SOR.
Put a defender in front of the board
and see how that alters everything
too!!!
The smaller student will naturally
lower their COG by bending their
knees and widen the BOS by widening
stance. They may even lean towards
the oncoming force or align the LOG
within their BOS and at the front edge
to increase stability.
The crouched starts advantage is it
decreases stability making it faster to
disrupt equilibrium and get a fast
start. Having LOG at front edge of BOS
means on the gun the athlete quickly
removes hands and begins moving
forward over the start line