Well if the rock doesn't move, then there is no amount of work done. There is no work done on an object if a force is applied to the object but it DOES NOT change its position, in this case is the rock.
2. The zeros in front do not matter
From equation of motion v^2 = u^2 +2aS
Hence, the final velocity is 40 m/s.
<em><u>hope </u></em><em><u>it's </u></em><em><u>help </u></em><em><u>you</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>.</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>!</u></em><em><u>! </u></em>
<em><u>#</u></em><em><u>rishu</u></em>