Regents Biology 2015/2016

[ Levers in human

body ]

Mohamed M.Elsaied

2016/2017

Supervised by :- Dr. Abouzeid A.Thabet

Allied Medical Science

Biomechanics

Introduction

Mohamed M.Elsaied

2016/2017

When person is moving his leg - arms -any part of his body He depend on his Skelton system (muscle forces) by contraction or extension muscles.

In fact the bone in moving work as A lever

Levers cannot be changed, but they can be utilized more efficiently .

levers

Mohamed M.Elsaied

2016/2017

Definition of levers

A rigid bar that turns about an axis of rotation or a fulcrum .

Parts of a lever

- Fulcrum Axis of rotation of the lever .- Effort Arm The part of the lever that the effort force .

- Resistance Arm The part of the lever

that applies the resistance force .

Classification of levers

Mohamed M.Elsaied

2016/2017

First Class Lever A first-class lever is a lever in which the fulcrum (Axis) is located

between the input effort (Force) and the output load (Resistance).

Second Class LeverResistance (load) is located between the effort arm and the

fulcrum .

Third Class LeverThe effort force is located between the fulcrum and the resistance .

The 3 Classes of Levers

Mohamed M.Elsaied

2016/2017

| Resistance Arm |

| Force Arm |

A

F R

| Force Arm | | Resistance Arm |

A

R| Resistance Arm | F

A

R

| Force Arm |

F

• FAR

1st

• ARF

2nd

• AFR

3rd

1 st class of lever in human body

Mohamed M.Elsaied

2016/2017

The joint between the skull and the atlas vertebrae of the spinethe spine is the fulcrum across which muscles lift the head .

Mohamed M.Elsaied

2016/2017

The joint between the hummers and radius – ulna .

2 nd class of lever in human body

Mohamed M.Elsaied

2016/2017

The Achilles tendon, pushing or pulling across the heel of the foot .

Mohamed M.Elsaied

2016/2017

3 rd class of lever in human body

Mohamed M.Elsaied

2016/2017

The elbow joint: when lifting a book, the elbow joint is the fulcrum

across which the biceps muscle performs the work.

Mohamed M.Elsaied

2016/2017

Benefit from lever ?

Mohamed M.Elsaied

2016/2017

Increase power

Increase distance

Increase speed

Transfer power from one place to another

precision in work safety

Avoid risks

Reference

Mohamed M.Elsaied

2016/2017

www.dynamicscience.com.au/tester/solutions/hydraulicus/simplemachineslevers1.htmhttp://www.montgomery.k12.ky.us/camargo/Projects/simplemachines/simplemachines.htm

http://www.dynamicscience.com.au/tester/solutions/hydraulicus/humanbody.htm