2 1 Lever systems examples of their use

2. 1 Lever systems, examples of their use in activity and the mechanical advantage they provide in movement.

Thinking of every day situations, how many examples of levers can you think of? **DISCUSS your answers with a partner then feedback to the group** TASK 1

How does the body use levers to bring about movement?

You will need to identify and describe… …the difference between: • FIRST CLASS • SECOND CLASS • THIRD CLASS levers • Explain the MECHANICAL ADVANTAGE of levers • Explain the DISADVANTAGE of lever systems • Analyse the use of lever systems in a physical activity.

Levers consist of four components: 1. 2. 3. 4. LOAD- this is the object requiring moving EFFORT- this is the muscular force we use to move the object FULCRUM-this is the joint around which the movement occurs LEVER- the bones of the skeleton are the levers

Levers The joints of our skeleton not only allow movement, they also act as LEVERS. The function of levers are to increase the speed at which a body can move.

Levers The human body is a system of levers and pulleys which enables us to move. • The joint itself is the fulcrum (Pivot). • This fulcrum 'takes the strain' of pulling one near, or away from another bone.

Levers The levers rotate around a series of joints. The force is provided by the muscles attached to the bone (think of the muscles acting as pulleys). The resistance comes from body weight and any implement used for sport (e. g. a bat or racquet).

Class of lever Levers can be classified as: • First class • Second class • Third class

Class of lever – First Class This is a lever where the Fulcrum (pivot) occurs between the effort and load. Effort Load Lever Arm Fulcrum TASK 2: Replace the labels on this diagram to replicate what is happening when we nod our head.

Class of lever – First Class The head is a good example of the action of a first-order lever in the body when the head and neck are being flexed and extended, as in nodding. Muscles in neck contracting Weight of head Neck joint First class levers can increase both effects of effort and the speed of a body.

Think of as many sporting examples as you can where a ‘flick’ or nodding of the head is important… As many as you can in 1 minute! * Discuss answers as a group to add more to your own list! *

Class of lever – Second Class This lever occurs when the load is between the effort and the fulcrum. Load Lever Arm Effort Fulcrum

Class of lever – Second Class When you raise up on to your toes you are using a second order lever. Weight of body and gravity Muscle working Ankle joint The foot is the lever bar. Second class levers tend to increase the effect of the effort force.

Think of as many sporting examples as you can where a second class lever is used. Work with the person next to you to ‘think, pair, share’ your ideas. As many as you can in 3 minutes! * Discuss answers as a group to add more to your own list! *

Class of lever – Third Class This lever occurs when the effort lies between the fulcrum and load. This is very common in human movement Load Lever Arm Fulcrum Effort

Class of lever – Third Class In terms of applying force this is a very inefficient lever, but it allows speed and range of movement. An example within the body is a bicep curl during flexion. The weight Arm Elbow Bicep muscle Third class levers can be used to increase the speed of a body.

• • Draw the following examples as a lever system in your books: Hitting a forehand hit with a tennis racquet Performing a free hit in hockey The action at the hip when we walk The action at the knee when we kick a football

How do I remember all of the levers? ? 1. 2. 3= F. L. E! 1 st class lever= Fulcrum is in the middle 2 nd class lever= Load is in the middle 3 rd class lever= Effort is in the middle

Mechanical Advantage The body’s levers can be made even more effective by using rackets, oars, paddles, sticks and bats.

Mechanical Advantage These pieces of equipment increase the length of the resistance arm of the lever. This in turn increases the speed at the end of the lever.

Mechanical Disadvantage Most levers in the body are third class levers where the resistance arm is always greater than the effort arm (mechanical disadvantage). The longer the resistance arm of the lever, the greater the speed at the end of it. So when bowling or passing a ball the performers arm should be fully extended to generate the most force and with the greatest speed.

RECAP Lever systems can be used to: • Move a heavier load • Move a load further and faster Mechanical Advantage Lever systems allow you to lift a heavier load and are said to provide a MECHANICAL ADVANTAGE. An example of this is a car jack that will only lift a car (the load) a small distance, but requires relatively little effort. Mechanical Disadvantage Lever systems where a greater force needs to be applied than the load to move provides a MECHANICAL DISADVANTAGE. An example of this is a drive in badminton, or a forehand hit in tennis- think of the speed and force generated on the shuttle cock and the power required to generate that.

Looking back… Take a look back in your notes and see which lever system is said to have a mechanical advantage as opposed to a mechanical disadvantage. The lever system that has the EFFORT further than the LOAD from the FULCRUM had an advantage. The lever system that has the EFFORT nearer than the LOAD to the FULCRUM has a disadvantage.

Apply it! What has stuck with you? Label the following levers components. Describe the 3 levers in the body (use diagrams to help illustrate your answer) Levers and mechanical advantage Explain the term ‘mechanical advantage’ Which class of lever always has a mechanical disadvantage?

Practice it! Exam questions 1. Which one of the following describes a second class lever system? A B C D (1) The load is at the right-hand end of the lever The fulcrum is in the middle of the lever The load and the fulcrum are at the same point on the lever 2. Label the lever system below (4) Lever class = ____________ ______

Practice it! Exam questions 3. Which one of these shows how to calculate the mechanical advantage of a lever? (1) A B C D Effort arm x weight (resistance) arm Effort arm ÷ weight (resistance) arm Effort arm + weight (resistance) arm Effort arm - weight (resistance) arm

Practice it! Exam questions 4. Analyse how the following parts of the lever system allow the weight trainer in Figure 5 to lift the weight. (i) Fulcrum (ii) Effort (2)

Practice it! Exam questions 5. Figure 4 shows a basketball player jumping to execute a shot. Draw the lever system which operates at the ankle joint in the space below. Label the fulcrum, effort and load. (1)

Practice it! Marks Scheme: 1. 2. 3. 4. Load Effort Fulcrum C i) Third class lever B One mark for linking bone or muscle to component of lever system and one mark for linking this to its use in the biceps curl to lift the weight. For example: Fulcrum – elbow is the fulcrum (1) which allows the arm to bend/flex (1) Effort – biceps muscle provide the effort (1) which allows the weight lifter to lift the weight (1)

Practice it! Marks Scheme: 5. Award one mark for labelling the effort, load / resistance and fulcrum in the correct order.