The mechanics in biomechanics презентация

Outline Mechanics and its application to biological systems Forms of motion Levers Balance and center of gravity

How Did It Walk?

How Did It Walk?

Mechanics and Biomechanics Mechanics: science that deals with physical energy and forces and their effect on objects Biomechanics - study of the mechanics as it relates to the functional and anatomical analysis of biological systems and especially humans

The First Class of Levers First class Levers In a first class lever the fulcrum is between the effort and the resistance. This type of lever can increase the effects of the effort and the speed of a body. Also good for keeping balance.

First Class Lever

The Second Class of Levers Second class levers Here the resistance is between the fulcrum and the effort. This type of lever is generally thought to increase only the effect of the effort force.

Second Class Lever

The Third Class of Levers Third class Levers Here the effort is between the fulcrum and the resistance and can be seen in the. They can increase the body’s ability to move quickly but in terms of applying force they are very inefficient.

Third Class Lever

Human Body Levers Human’s levers are mostly built for speed and range of movement at expense of force Thus, short force arms and long resistance arms require great muscular strength for movement Examples: biceps and triceps attachments biceps force arm is 1 to 2 inches (1inch=2.54cm) triceps force arm is less than 1 inch

Example 1. How much force (in kg) needs to be applied to move 45 kg when the RA is 0.25 m and the EA is 0.05 meters? Use the formula FE x EA = FR x RA Note: kgs are not units of force, but sometimes force is divided by g(9.8m/s2) and expressed in kilograms.

Example FE x 0.05 meters = 45 kg x 0.25 meters FE x 0.05 = 11.25 kg FE = 225 Kg

Lever Length Where is the velocity or speed the greatest; at A’ or B’? How can this principle be applied to tennis?

Lever Length A longer lever increases the speed at the end of the racquet unless the extra weight is too great. Then the speed may actually be slower.

Stability Center of gravity (CG): Point at which all parts of a body are equally balanced Base of support (BOS): Area within an object’s point of contact with the ground Line of gravity (LOG): Direct line from the center of gravity to the ground

Center of Gravity

Base of support The BOS area can be changed Larger BOS area is typical for more stable positions In humans, wide BOS is usually accompanied by low CG

Line of Gravity The line of gravity is always vertical The LOG must outside the base of support to initiate or continue movement The further away the LOG from the BOS, the greater the tendency to move in that direction

Stability Someone is more __________when they have a _______centre of _______, a ______ base of __________ and a line of gravity that falls _______the body.

Advantages/Disadvantages to Bipedal Locomotion Disadvantages Loss of speed Loss of agility Loss of stability Advantages Carry food Carry tools Increased ability to nurture/protect offspring

Interesting Fact: T Rex Arms How much could T Rex lift with its arm? (50x6=300lbs 136kg) ?