Question

Step 1 Expression for work done by the frictional force on an object is, Here, k is coefficient of kinetic friction, m is mass of object, g is gravitational acceleration, and d is displacement, Work done is path dependent parameter. In the given case, the person put the box at starting position. Hence, the displacement of the box is zero. Therefore, the work done by the person on the box 1S Zero Thus, the correct option is

Answer 1

See that when person pushes on the floor there will force by friction, which will given work due to friction force. But when he carries it back to the starting point in air then there will be no friction force, So in that case work due to friction will be zero.

Since, W_net = W_friction + W_person + W_lifting So, given total displacement is Zero, W_net = 0 & also box is pulls up & put down, so W_lifting = 0 Therefore W_person + W_friction = 0 rightwardsdoublearrow W_person = -W_friction Here, W_friction = F_r times d times cos(180 degree) Where, friction force (F_r) = mu_k times N = mu_k mg So, W_friction = mu_x times mg times d times (-1) = -mu_k mg d Therefore, Work done by person, W_person = -(-mu_k mg d) rightwardsdoublearrow W_person = mu_k mg d

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