Levers

To begin with ...Challenge time!

What do you need to know?

Levers

Can you stand with your heels touching the wall and then pick up the object in front of you?

It is impossible to pick up the object because the person becomes unbalanced

Thinking Points

How can we overcome this problem?

How do things normally balance?

How can we calculate if something will balance?

• components of a lever
• classify different orders of levers (1st, 2nd, 3rd)
• Draw diagram of each
• sporting examples
• efficiency of each system (mechanical advantage equation)

Mechanical advantage

equation

Mechnaical =

advantage

Effort arm

Resistance arm

The mechanical advantage of a lever system depends on the distance between the effort and the fulcrum (known as effort arm)when compared to the distance between the fulcrum and the load (resistance) known as the Resistance arm. The mechanical advantage is worked out by dividing the effort arm by the resistance arm:

MA = Effort arm ÷ Resistance arm

Having a short effort arm allows for faster movements over a larger range whereas having a short resistance arm allows a heavier load to be lifted.

Using 3rd class levers in sport

Analysis of 3rd class levers in sport

PPQ 2018

Advantages:

Analyse the mechanical advantages and

disadvantages of using a third class lever in

sport. (4)

• greater range of movement due to long resistance arm
• Speed of load is faster than speed of effort
• Resistance can be moved quickly because force is applied close to the fulcrum.

If we think of 3rd class levers the effort is always close to the fulcrum therefore has a short effort arm.

The resistance is always futher away from the fulcrum therefore has a long resistance arm.

Disadvantages:

• effort arm is short so muscles unable to produce much force
• Performer struggles to move heavy loads

Effort is closer to the fulcrum than the resistance

Effort arm

Resistance arm

REFLECTION TASK

Resistance/

load

What does this word mean?

When levers are put into diagrams, they look like this:

Introduction

Complete the table, by drawing the levers and identifying them....

Resistance

Effort

TASK

Fulcrum

Name and sketch the lever operating at the elbow - remember tricep is the only muscle which inserts above the joint that it works

Resistance

Fulcrum

Effort

Fulcrum in the middle

= 1st order lever

Effort

Fulcrum

Remember : effort is the point where the muscle is inserted (all muscles insert below the joint, except for the tricep muscle which inserts above)

TASK

Name and sketch the lever operating at the ankle

Levers

This is one of the few 2nd class levers in the body.

TASK

Even though it's asking about the ankle, the fulcrum is at the toes, the effort (gastrocnemius), resistence (body weight), causes plantarflexion of the foot

Can you think of examples from sport of when a performer goes on their tip toes?

Resistance

These are all 2nd class levers

Task

A lever is a rigid bar that rotates around a fixed point and is used to apply a force against a resistance

Effort

Fulcrum

Name and sketch the lever operating at the knee

Levers in the body consist of a muscle, a joint and a weight being lifted

PIVOT = FULCRUM

Resistance

Three classification

of levers

(weight)

Levers are classified according to what's in the middle of the lever (fulcrum, effort, resistance)

Main terms

Joint = Fulcrum/pivot

Muscle = Effort

Weight = Resistance/load

Effort

Other words we need to be aware of are: Effort and load/resistance

1 2 3

F R E

(quadricep

insertion)

it's a little rhyme!!

We can use a ruler to help work out the order

Effort in the middle = 3rd order lever

Fulcrum

(knee)