A 2kg object accelerated as a net force acts on it. During the 5 seconds this force acts, the object velocity changes from 3 m/s east to 7m/s west. The initial kinetic energy of the object was 9 joules, and the final kinetic energy was 49 joules

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