Question

when we lift a body against gravity th work done is said to positve while when we put the body towards the earth the work done is said to be negative ?
my question is when a body is lifted against the gravity it should give negative work done while is gives positive wd..??????

Answer 1

Actually your question is a bit unclear.
What are you referring to exactly as in - Work done by gravity or the work done by the external force applies by us?

Answer 2

it depends upon which direction u take the +ve and -ve on an axis.
in the first case u have taken gravity to be posititve in the upward direction, thus it is negative in the downward direction. it is a matter of choice, u can take and upward/downward direction to be +ve or -ve.
But u have to keep that assumption constant throughout the problem. it has to be constant.