What is the mass of the sleigh if it moves under the action of a force of 30N with an acceleration of 4 M / s2 coefficients

What is the mass of the sleigh if it moves under the action of a force of 30N with an acceleration of 4 M / s2 coefficients. friction on snow 0.2.

We express the weight of the sleigh from the ratio:
m * a = F – Ftr, where m is the mass of the sleigh (kg), a is the acceleration of the sleigh (a = 4 m / s²), F is the force that acts on the sleigh (F = 30 N), Ffr is the friction force ( Ffr = μ * N = μ * m * g, where μ is the coefficient of friction (μ = 0.2), g is the acceleration of gravity (we take g = 10 m / s²)).
Let’s calculate the weight of the sleigh:
m * a = F – μ * m * g.
m * a + μ * m * g = F.
m (a + μ * g) = F.
m = F / (a + μ * g) = 30 / (4 + 0.2 * 10) = 30/6 = 5 kg.
Answer: The weight of the sleigh is 5 kg.