164. According to the figure below, a body is at rest on a horizontal surface. A horizontal force $F = 40\,\text{N}$ is applied to the body. After $5$ seconds, the force $F$ decreases to $30\,\text{N}$. How does the body move after that? $$\left(g = 10\,\frac{\text{m}}{\text{s}^2}\right)$$
[Figure: A block of $2\,\text{kg}$ on a surface with $F = 40\,\text{N}$ applied horizontally; $\mu_s = 0.6$ and $\mu_k = 0.5$]

• [(1)] The body stops at that instant.
• [(2)] The body moves with acceleration $1\,\dfrac{\text{m}}{\text{s}^2}$.
• [(3)] The body moves with acceleration $2\,\dfrac{\text{m}}{\text{s}^2}$.
• [(4)] The body continues moving at constant speed.