Okay let me just write here a in a black marking panel just to raise the the what i'm what i'm about to write now so ladies and gentlemen because we know what net is equals to that we know work as a result of tension it's acting upwards okay and we've got two forces which are acting in the opposite direction which is minus work as a result of gravitational force minus work as a result of fractional force all of these is equated to zero obviously if you've seen why this is equated to zero is because of constant speed okay so ladies and gentlemen.
I've already indicated the signs over there that this is
going upwards this is coming a downwards that's if i've assumed a upwards to be
positive downwards to be negative which makes it easy that way okay so the cost
angle there it has got not that much impact but just to give the direction okay
so that means if you punch on a calculator cos one you i mean cos zero you
might find that it's positive one so that positive one is multiplied by that t
and one eight it just gives you nineteen thousand two hundred if you punch cos
180 you might find that it gives you negative one that negative one is
multiplied by all of this.
Okay it doesn't really make any difference other than the
you know having an impact on the sign okay very very much important ladies and
gentlemen so now let's check a in this case it means over there it actually
should be a negative okay but because we said net and net means total total
means add okay that means our final answer for this must be a negative value in
joules okay which indicates that a work as a result of friction it's actually
acting downwards okay so it serves as a hint in terms of guiding us if we are
heading towards the right direction or not so that means if we get a positive
answer then something is wrong okay so ladies and gentlemen what you do now is
just to say 19 a 19 200 minus 15 a thousand six hundred and eighty.
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