3.1 CHANGES IN SPEED:
The opposite is true if we want to decrease the speed of a rotary system.We must transmit motion from a smaller element to a larger element.If the input and output elements are the same size,the rotary speed remains constant.The rotary force will also remain constant.

• pulley1: D1)D2   N2)N1

• pulley1: D1=D2  N2=N1

• pulley1: D1(D2  N2(N1

3.2 SPEED RATIOS:
D1=30mm 
D2=10mm

 
  


 The relationship between the speeds of the two wheels is inversely proportional to their sizes.  
N2/N1=D1/D2
This relationship is called the ratio of tranmission,where N is the speed of rotation and D is the diameter of the wheel.  

3.ROTARY TRANSMISSION:
Rotary tranmission system put two rotating elements into contact.These mechanisms have two purposes:

• Friction wheels:  

• Pulleys with belts: 

• Interlocking gears:

All of these mechanisms keep the same speed retios,but each one offers a different advantage.
uses:friction wheels and pulleys are often used intoys and other devices with moving parts,such as industrial rollers or conveyor belt systems.Gears are used in clocks,while sprockets and chains are common in home appliances.

COMPOUND PULLEY SYSTEMS:
A compound pulley systems is a combination of fixed and movable pulleys.It is also called a block and tackle system.The more pulleys there are,the less force we need to lift the load.We can combine the pulleys in various ways.

• VERTICAL SYSTEM: 
  
  
  
  
  HORIZONTAL SYSTEM:

EXPONENTIAL SYSTEM:

2.2 PULLEYS AND COMPOUND PULLEY SYSTEMS:
In a system of pulleys,the equilibrium between the forces depends ion the parth that the rope follows.

PULLEYS:
Fixed pulley:the forces are equal because the rope moves the same distance on both sides.We can use gravity and our own weight to help us.It´s easier to lift a weight by pulling down than by pulling up.

 Movable pulley:the rope follows a double path around the pulleys.We need half the force to lift the same weight as with a fixed pulley.We must pull twice as much rope to lift an object to the same height.

 

BRAKE LEVERS:
Bicycle brakes decreased speed.

A HAND CRANK:
A clank is a class2 lever,so it obeys the law of the lever
F-is the force that we apply
D-distance from the axis of rotation
R-in the shaft.

BICYCLE HANDLEBARS: 
If we put our hands near the middle,it´s more difficult to turn the handlebars.It is easier to turn a larger steering wheel becouse there is a larger distance between the outside of the wheel and this axis of rotation in the centre. 

 

2. LINEAR TRANSMISSION OF MOTION:
Linear transmission mechanisms,such as pulleys,use linear motion inut to produce linearmotion output.

2.1 LEVERS:
A lever is a rigid bar that turns around a point called a fulcrum.
Each force prodeces a specific torque,which is the force multiplied by its distance from a fulcrum.
 When the forces acting on opposite ends of a lever are equal,we say the lever is in equilibrium.We can express this mathematically as the law of the lever.

                         F+d=R+r


CLASSES OF LEVERS:
We can divide levers into classes according to the locations of the fulcrum,force and resistance.

Class2:levers increase the fore that we apply
Class3:levers incrase the distance that the end of the lever moves.
Class1:levers can do both of those things.

 

TEMA 5

1.0 WHAT IS A MECHANISM?
The moving parts of a bicycle are examples of everyday mechanisms that make life easier and more enjoyable:

• The chain of a bicycle transfers motion to the back wheel
• The bar of a seesaw forms a lever that we can use for fun
• The gears inside old-fashioned clocks let us measure time
• The pulley systems above a well helps us to bring up later

They make work easier because they transmit and transform force and motion.All of these mechanims require an input force and motion from some type of source.In the case of a bicycle,our leg muscles are the input source.Mechanims transmit motion and force to receptors that finally perform the work.This is the output force nd motion.In the case of an analogue clock,the output receptors are the hands of the clock that move in circles to show the time.

1.1 THE PARTS OF A MECHANISM:

Mechanisms transmit and transform force and motion from an input source to an output receptor.This transmission and transformation lets us perform different types of work with more comfort and less effort.

Imput of force and motion.-----Mechanisms------Output force and motion.