What would be the amount of work done on an object by a force,if the displacement of the object is zero?

At what speed will a body of mass $1\, kg$ have a kinetic energy of $1\, J$ (in $, m/s$)?

$(i)$ State the law of conservation of energy.
$(ii)$ Show that the total mechanical energy of a freely falling body is conserved.

Justify giving proper reasoning whether the work done in the following case is positive or negative: Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.

When is the work done by a force said to be negative? Give one situation in which one of the forces acting on the object is doing positive work and the other is doing negative work.

$(a)$ What is meant by mechanical energy? State its two forms. State the law of conservation of energy. Give an example in which we observe a continuous change of one form of energy into another and vice-versa.
$(b)$ Calculate the amount of work required to stop a car of $1000 \, kg$ moving with a speed of $72 \, km \, h^{-1}$.