Final Answer:
The acceleration of the block at this instant is approximately 4.18 m/s² to the left.
Step-by-step explanation:
The acceleration of the block can be determined through the following steps. First, consider the forces acting on the block. The spring force, given by Hooke's Law (F_spring = -kx), opposes the direction of compression. The kinetic friction force (F_friction = μ_k N) acts opposite to the direction of motion.
The net force (F_net) is the sum of the spring force and the friction force. Applying Newton's second law (F_net = ma) and considering the negative sign for forces opposing motion, the equation becomes ma = -kx - μ_k x N. The normal force (N) is equal to the gravitational force acting on the block (N = mg).
Substituting this into the equation, we get ma = -kx - μ_k x mg. Solving for acceleration (a), we find a = (-kx - μ_k x mg) / m. Plugging in the given values, we get a = (-700 x 0.02 - 0.12 x 5 x 9.8) / 5, resulting in an acceleration of approximately 4.18 m/s² to the left.