Work
A farmer ploughing the field, a construction worker carrying bricks, a student studying for a competitive examination, an artist painting a beautiful landscape, all are said to be working. In physics, however, the word ‘Work’ covers a definite and precise meaning. Work refers to the force and the displacement over which it acts. Consider a constant force `F` acting on an object of mass `m`. The object undergoes a displacement `d` in the positive `x`-direction as shown in figure.
The work done by the force is defined to be the product of component of the force in the direction of the displacement and the magnitude of this displacement, thus `W=(F cos theta)d = F•d.`
In which case, work done will be zero?
Options:
(a) A weight-lifter while holding a weight of 100 kg on his shoulders for 1 min
(b) A locomotive against gravity is running on a level plane with a speed of `60 kmh^(-1)`
(c) A person holding a suitcase on his head and standing at a bus terminal
(d) All of the above