Let the Force be F
mass = 5 kg
time(t) = 10 s
initial velocity(u) = 3 m/s
final velocity(v) = 7 m/s
so let the acceleration be a
so a = (v - u)/t = (7 - 3)/10 = 0.4 m/s²
So the magnitude of the applied force,
F= m*a
=5*0.4
=2 N
and the final velocity after 5 s is v
so v = u + at
v = 3 + 0.4 x 5
v = 5 m/s
The final velocity after 5 s is 5 m/s