How to find the speed if a 1 kg bar moves with an initial speed of 6 m, s. A force equal to 2 N

How to find the speed if a 1 kg bar moves with an initial speed of 6 m, s. A force equal to 2 N is applied to the bar, and the coefficient of friction between the bar and the table is 0.3. Find the speed in 5 seconds.

V0 = 6 m / s.

m = 1 kg.

g = 9.8 m / s ^ 2.

F = 2 N.

μ = 0.3.

t = 5 s.

V -?

Let us write Newton’s 2 law in vector form: m * a = F + Ftr + N + Ft, where m is the mass of the bar, a is the acceleration of the bar, F is the force with which it is pulled, Ftr is the friction force of the bar, N is the support reaction, Ft is the force of gravity.

Let’s write 2 Newton’s law in projections on the axis.

OH: m * a = F – Ftr;

ОУ: 0 = N – Fт.

The force of gravity Ft and the force of friction Ftr are determined by the formulas: Ft = m * g, Ftr = μ * N.

m * a = F – μ * m * g.

a = (F – μ * m * g) / m.

a = (2 H – 0.3 * 1 kg * 9.8 m / s ^ 2) / 1 kg = – 0.94 m / s ^ 2.

the sign “-” means that the acceleration is directed in the opposite direction of motion, the body is decelerated.

a = (V – V0) / t.

V = V0 + a * t.

V = 6 m / s + (- 0.94 m / s ^ 2) * 5 s = 1.3 m / s.

Answer: the speed of the bar will become V = 1.3 m / s.