hello and welcome to this exam question video we're looking at aqa gcc pe today and we're in
this past paper looking at question 19.2 and 19.3 because they go quite nicely hand in hand and what
it's asking us is to identify the type of lever from this image up here now this could be from
any sporting context but you need to be able to sort of analyze a movement work out what joint
is is moving and articulating what muscles and agonists and antagonists are in action
and then from that you'll be able to work out the lever system in play so we're looking at
this forehand tennis stroke and we're looking to identify the type of lever being used at the elbow
and then at the end what we'll do is look at how to label not just this lever but all three of them
so i'm going to jump into the whiteboard just to make this a little bit clearer and firstly what
i'm going to put onto the board here is a little rhyme which we can remember which can help us
remember the lever systems which is fle123 now in this little rhyme we get what three different
three pieces of information we get the different systems there are there's three different systems
we get the three components of the system and we get the order that these components should go in
to comprise a specific type of lever so three things from this little rhyme the components how
many there are and what order the components going to make up different systems and what we notice
is that the letter corresponds to the central component so a first-class lever system
the number one is a lever system where the fulcrum is in the middle a second-class lever
system is when the load is in the middle and the third class lever system is when the effort is
in the middle so if we were to just sort of picturize these to start with we'll go with
the first class leave the system and we start with the fulcrum in the middle which is our f
we then have the the rigid bar and then the other two components the load and the effort they can go
in either order it doesn't matter which way around they go you just need to draw it so that the
the system makes sense so obviously the load is where gravity or resistance would be acting
so the load would be working down on this side and in order to pull a bone in order to overcome
this this resistance obviously we would either want to be pulling downwards on this side in order
to move this load upwards or it would be pulling from the other side if we were to be lowering it
down but we're not concerned about that we're concerned about overcoming the resistance so
we would have the effort over here the load on this side and the fulcrum in the middle for a
first-class lever system if it were a second-class lever then we need to put the load into the middle
so we draw the load first and we know that's going to be acting downwards through the rigid bar of
the bone and then it doesn't matter which end the other two go so if we draw the fulcrum at this end
to that pivot point and in order to overcome the resistance there's no point pulling the
effort down through the bar we would be pulling away and upwards so that we can sort of lever
this box this load upwards off the ground now it's important to note in sort of everyday life
this effort could be applied from underneath so we could draw it from that direction but this would
be for example a wheelbarrow where a person is pushing upwards from underneath the metal
structure and pushing with effort upwards through that end but in the body muscles can only pull
on a bone they can only shorten in order to move the bone they can lengthen to allow for movement
during eccentric contractions but what we're concerned more about here is overcoming resistance
in concentric contraction so a muscle can't push it can only pull so the way that i picture lever
systems in the body is that this arrow is in fact the the muscle tendon so the rigid line is the
bone the point of contact is the insertion or the origin of the muscle tendon on the bone itself and
then the arrow is well the tendon and the muscle so if we were to contract this green arrow and
shorten it in on itself what would happen well it would lift upwards and the bar would move with it
as would the load so a way to remember it is to draw the arrow going away from this rigid
bar because that's how muscles in the body work now in everyday life an effort could be working
in the direction of the metal bar but muscles don't do that so insert the tendon onto the bone
and then pull it away and then if we were to do that obviously this would be
a system number one would be like a catapult and system number two is a bit like a wheelbarrow if
you were to pull upwards from above that metal structure and the same goes for our third class
lever so third class we're looking to have the effort in the middle so we have our rigid bar
we have our effort pulling this bone upwards and then for it to make sense the fault comes
obviously underneath and the load would be on top with gravity working down so the load would
be there the effort would be in the middle as per our rhyme and our fulcrum would be here at the end
so the tennis stroke or if we draw that action out so we could go back to the question itself
identify the type of lever being used at the elbow during the forehand tennis stroke so from
position a through to position b we're talking about elbow flexion so if we come back now and
think about what an elbow does in order to flex or to decrease the angle we quickly draw the bones
and the bones themselves we've got the uh the humerus up at the top here and then we've got the
radius slash ulna as part of the lower arm now on top we would have the bicep
on top of the humerus and most importantly the tendon of the bicep inserts onto the articulating
bone there so that point of contact which we've spoken about here and here and here that point
of contact and then the direction of that pull is that arrow so we know that that there is the
effort part of this lever system now what about everything else well we know that the elbow joint
is here because that is where the radius is going to be pivoting on the end of the humerus and we
know that the racket or the hand or the resistance is going to be at the other end of the bone so if
we were to take a bit of a zoom in of that what would we be looking at we'd be looking at the
radius armor we'd be looking at the hand slash racket slash ball shot slash resistance
we've got the effort in the middle and we've got the fulcrum at the end so the
effort is in the middle f l e oops fle123 we know it's the third class lever system
the load is at this end and the fulcrum is there so tennis stroke or the forehand tennis stroke in
in tennis at the elbow is a third-class lever system and this is how we would draw l
e f load load at one end effort in the middle which is being caused by the bicep contracting and
the fulcrum at the end which is the elbow joint of the humerus radius and ulna and that's that
quite a quick way to pick up one mark from this question just to identify as the third class lever
and then two additional marks to get the three different components labeled correctly as part of
the lever system i hope you found it useful and i'll see you again in the next one bye for now
bye