Calcular la masa de un cuerpo que, estando en reposo, se le aplica una fuerza de 150 N durante 30 seg, permitiéndole recorrer 10 m. ¿Qué rapidez tendrá al cabo de ese tiempo?​

  v = 0.667 m / s,   m = 6746 kg

Explanation:

For this exercise we must use the relationship between work and kinetic energy

          W = ΔK

 the work is defined by

          W = F. x

bold indicates vectors

          W = F x cos θ

in this case the force is in the same direction of displacement

          W = F x    

         F x = K_f - K₀

as the body starts from rest the initial kinetic energy is zero

         F x = ½ m v²

Now let's use the relationship between momentum and momentum

        I = Δp

        I = F t

        Δp = m v_f - m v₀

as part of rest v₀ = 0

        F t = m v

Let's write our system of equations

         F x = ½ m v²

         F t = m v

we have a system of two equations with two unknowns, let's divide the two expressions

         x / t = ½ v

         v = 2x / t

         v = 2 10/30

         v = 0.667 m / s

we look for the mass

         F t = m v

         m = F t / v

         m = 150 30 / 0.667

         m = 6746 kg

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .