Find the work done in pulling a 120 gram box in an incline plane, 150 cm long and 90 cm high if the coefficient of friction is 0.25.
Your teacher is just too easy.
work done=netforce * distance
net force is work done against friction plus work done against gravity. In either case, it is force*distance*cosine of the angle between.
Gravity: downward force, distance is .9m, and the angle between is arctan90/150
work done on gravity: .120*g*.8cos(arctan 9/15)
you can use your calculator on that.
workdone on friction.
friction work= forcenormal*mu*distance
= mgCos arctan9/15*mu*.9*cos arctan 9/15
so grab your calculator and add.