A child pushes horizontally on a box of mass m which moves with constant speed v across a horizontal floor. The coefficient of friction between the box and the floor is µ. At what rate does the child do work on the box?

Explanation:

mas of box = m

velocity = v

coefficient of friction = μ

Force = coefficient of friction x Normal reaction

F = μmg

rate of doing work is called power, so

P = Force x velocity

P = F x v

P = μmg x v

P = μmgv

"i have always loved contemporary art and made it a general goal to work within the field. after a few nonprofit internships at museums and galleries, i decided to try the for-profit art world and was offered a job as the ad assistant at the magazine. i much prefer the pace of the for-profit art community and have stayed with the company for three years, with a promotion to an account manager last spring."

i just did this and got a 100.