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.