Answer:
[tex]k_f[/tex] = 40J
Explanation:
The work and energy theorem says that:
[tex]W_f =k_f-k_i[/tex]
where [tex]W_f[/tex] is the work of the force, [tex]k_f[/tex] the final kinetic energy and [tex]k_i[/tex] the initial kinetic energy.
Addittionally, the work of the force is calculate as force multiply by distance and if the crate inittialy is at rest, the initial kinetic energy is zero, so:
[tex]Fd = k_f[/tex]
where F is the force and d the distance. Then, replacing values, we get:
[tex](10N)(4m) = k_f[/tex]
[tex]40J = k_f[/tex]
it means that the system gain 40J of kinetic energy.
