a ball of mass 0.2kg is thrown vertically upward by applying a force by hand. if the hand move 0.2 metre above while applying the force and bal;l goes to distance 2. find f
62It is a wonderful question...
It is like the body is accelerating due to a force
then retarding due to gravity..
so you have to take these two into consideration....
The displacement of the first part is 0.2
Then u find the velocity.. just at release..
Then again the displacement.
i think this should do...
There is a simpler mehotd u can think .. exactly the reverse...
find the initial velocity needed to make it move 2 m under gravity
if s=0.2 find the acceleration to take the body from rest to that velocity ....
and then F=m.a
1cant we think it this way...
work done by hand =F.s = 0.2F
work done by gravity = mgh =0.2X10X2
both equal.. so, F=20N
correct me,,, if wrong...
1i think u made a slight mistake skygirl
work done by gravity is not equal to mg*2
but equal to mg*(2+0.2)
as you are equating both w.r.t their initial and final states
work done by gravity in the whole process is equal to mg*(2+0.2) = 4.4
hence force =22N
dont forget that mg is also acting when the hand is applying the force
62Point taken dude :)
I was presuming that it was already accounted. But yeah my wrong :)
But yeah i really liked the approach
*To be true.. it din strike me until i read sky's soln.
1OH SHIT!
YES RIGHT...
THE HAND ALSO GOES UP.... SO DAT WILL BE ADDED..
BAD MISTAKE :(