excuse me i just want to ask something about mechanical engineering design
my teacher told me formula to calculate Power (P) is :

P = (F1 - F2) x v/102
F1 and F2 is tension of the belt (Newton)
v = velocity (m/s)

but when i look at mechanical engineering design book by khurmi there said the formula would be

P = (T1 - T2) x v
T1 and T2 is tension of the belt (Newton)
v = velocity (m/s)



what i want to ask is why there is two diffferent formula and what is the nominal 102 means??

can anyone here help me please

thank you