Hey guys what rule do you use for work??
I use Work by Driving force=change in p.e+change in k.e+work agnst resistance
Others use Work by D - Work agnst R = Final M.E - Initial M.E???
I know both are the same but which is prefered to be used as A RULE before substituting..
Another question..
When they ask for Loss in K.e..Do we give it as +ve loss or -ve(change) Do you get what I mean?? For ex: if they ask for change answer wod be -ve what if they ask for Loss we give as +ve right?? What abt the equation (rule( do we give it as 0.5m(u^2-v^2) or 0.5(v^2-u^2) then state its -ve because its loss??)
Plz answer me If you are sure 
Thank You ..
ok for ur first question , i had the same confusion, but i have learned that logic works best in this kind of problem, For example >
work is done by the driving force to overcome loss in ke and work done against resistance, because they are both actually working against letting an object move ryt? cuz ke is lost bcuz there was resistance.. do u get it? so work dont by driving force = Loss in ke + work done by resistive forces... secondly this formula >> work done by DF - Work done by Resistive forces = gain in KE , apply this to the situation, if u dont get the answer then u need to think logically about the changes invloved...
if u dont understand this, then PLEASE do ASK me again and i will give u specific example from pastpapers,
for ur second problem >>
u can change the formula from 1/2m(v^2 - u^2) to 1/2m(u^2 - v^2) .. we always write the value as postive no matter if its gain or loss
the first formula is for gain because final speed will be greater than initial speed so u subtract v^2 from u^2.
the second formula is for loss cuz obviously initial speed will be greater than final speed so u subtract u^2 from v^2 ..
do u get it?
