A 10 g block placed on a rough horizontal floor is being pulled by a constant force 50 N. Coefficient of kinetic friction between the block and the floor is 0.4. Find work done by each individual force acting on the block over displacement of 5 m.

Explanation

Given, mass m=10 g
Constant force F=50 N
Coeffcient of kinetic friction, `mu_(k)=0.4`
Displacement, s = 5m ,
Forces acting on the block are its weight (mg = 100).
Normal reaction (N=100 N) from the ground, force due to kinetic friction `(F=mu_(k)mg=40 N)` and the applied force (F= 50 N) which are shown in the given figure.
Work done `W_(g)` by the gravity, i.e., weight of the block `W_(g) = 0 J` `:'(mg bot s)`
Work done `W_(N)` by the normal reaction `W_(N)=0 J` `:' (N bot s)`
Work done `W_(F)` by the applied force `W_(F)=500xx5=250 J`
Work done `W_(f)` by the foece of kinetic friction `W_(f)= 40xx5`
`W_(f)=-200 J` (`:'` F and s are antiparallel)