WORKERS OF ALL LANDS UNITE

In physics, work done is the amount of energy transferred by a force.
Work Done = Force * Distance
When you move an object from one place to another, a positive work is done.
When you stop an object which was moving earlier, a negative work is done.
Basically when a force is significant enough to cause a change in energy (kinetic usually), then the work is considered done by that force.
W = F * D = F * D * cos theta.

To make the class interesting, physics teachers would always quote two things.
1. When you carry an object say a shopping bag at the behest of your mother and ask for a favour or pocket money in return, then the mother can simply reject your statement saying that according to physics you have not done any work. teta is zero- The class by now would burst into laughter.
2. But when you carry the same shopping bag to your mother's room upstairs, then you have done some work. theta is some angle.

I have my doubts in the spirit of the statement that translated into this formula.
a. When a car is stationed and you touch it. Work is not done because you are not responsible for the change in kinetic energy and in fact there is no change in kinetic energy of car. But when you carry a shopping bag, you have lifted the bag from the surface. If it isn't for you, the bag would have reached the ground. In effect, you are preventing a change in kinetic energy of the bag (gravitational energy converted into kinetic energy), thus changing the kinetic energy actually. (You might call this a potential energy)
b. If you argue point a is wrong, then you should very well accept point 2 is also wrong. Because in effect you are not changing the kinetic energy of the bag. You are just increasing the potential energy.
So my main argument is that when a force is applied work on the object will be done. Don't ask me to come up with a formula.

PS: I know i feel little lonely!!