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Answer the following:
In the above figure (i) the man walks $$2m$$ carrying a mass of $$15kg$$ on his hands. In figure (ii), he walks the same distance pulling the rope behind him. The rope goes over a pulley, and a mass of $$15kg$$ hangs at its other end. In which case is the work done greater?
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Solution
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In figure (i) the force applied by the man is perpendicular to the direction of movement of mass,i.e, $$\theta =90^{0}$$
$$W=Fs\cos\theta=Fs\cos90^{0}=0$$
In figure (ii) The force applied is in direction of the movement of mass i.e. $$\theta =0^{0}$$
$$\therefore W=Fs\cos\theta =Mgs\cos\theta$$
$$=15*9.8*2*1=294J$$.
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