Answer: The force is 4N to the west direction,
Explanation:
Let's define east as +x, and west as -x
The mass of the object is 2 kg.
During 5 seconds, the velocity changes from 3m/s to -7m/s
Now, by the second law of Newton we have that:
F = m*a
This means that the applied force is equal to the mass times the acceleration, and we also know that the integral of the acceleration is equal to the velocity:
a(t) = F/m
v(t) = F/m*t + v0
where v0 is the initial speed, in this case, 3m/s
v(t) = (F/m)*t + v0
at t = 5s, we know that the velocity is -7m/s
-7m/s = (F/2kg)*5s + 3m/s
-10*(2/5)N = F
-4N = F
This means that the force is 4N in the west direction.
The final statement about the kinetic energy does not give any information, because:
k = (1/2)*n*v^2
then
initial energy = (1/2)*2kg*(3m/s)^2 = 9 j
final energy = (1/2)*2kg(-7m/s)^2 = 49 J
