To move a stack of books across the table, a horizontal force of 32 N had to be applied to it. What is the mass of the stack

To move a stack of books across the table, a horizontal force of 32 N had to be applied to it. What is the mass of the stack if the coefficient of friction between the bottom book and the table is 0.4?

Initial data: F (force applied to a stack of books) = 32 N, μ (coefficient of friction) = 0.4.

Since the force applied to the stack of books is completely spent on overcoming the frictional force, the following relationship is true:
F = Ftr = μ * N, where N (the reaction force of the support, is numerically equal to the force of gravity acting on the stack of books) = m * g (g (acceleration of gravity, const) = 10 m / s2).

F = μ * m * g and m = F / (μ * g).

Let’s do the calculation:

m = 32 / (0.4 * 10) = 8 kg.

Answer: A stack of books weighs 8 kg.