A man starts walking from a point on the surf | vedclass

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(A) The work done by the man is $W = \int \vec{F} \cdot d\vec{r}$.Since the surface is assumed to be smooth,there is no friction force acting on the m

Vedclass · Accepted Answer

Zero

Vedclass · Answer

(A) The work done by the man is $W = \int \vec{F} \cdot d\vec{r}$.Since the surface is assumed to be smooth,there is no friction force acting on the man.The only force acting on the man is the gravitational force,which always acts towards the center of the Earth.As the man moves along the surface of the Earth,his displacement vector $d\vec{r}$ is always tangent to the surface,while the gravitational force $\vec{F}_g$ is always directed towards the center (normal to the surface).Since the angle between the displacement vector and the gravitational force is $90^{\circ}$ at every point,the work done by gravity is $W = \int F_g \cos(90^{\circ}) dr = 0$.Therefore,the net work done by the man is $0$.

$A$ man starts walking from a point on the surface of the Earth (assumed smooth) and reaches the diagonally opposite point. What is the work done by him?

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