Question

A block of mass 20 kg slides along a horizontal floor with an initial velocity of+23 ms . The coefficient of friction between the floor and the block is μk = 0.65.
Sketch the forces acting on the block, indicating their magnitude.

Answer 1

Three forces are acting on the block: gravity force $\mathbf{F}_g$, normal foce $\mathbf{N}$ and friction force $\mathbf{F}_{fr}$. Their magnitudes are:

$$F_g = mg = 20\cdot 9.8 = 196N\\ N = F_g = 196 N\\ F_{fr} = \mu_k N = 0.65\cdot 196 = 127.4N$$