The initial velocity of the block is 12.0 m/s east, as stated in the problem. This speed is the condition at t = 0 before the block experiences the westward acceleration that eventually reverses its direction.
The initial velocity of the block moving on a horizontal surface and sliding east with a speed of 12.0 m/s is already provided within the question's scenario. The block is subjected to a constant acceleration toward the west with a magnitude of 2.00 m/s², meaning the acceleration is in the opposite direction to the motion, hence causing the block to slow down.
The concept of constant acceleration is key in understanding the motion described in the problem. The provided details about the block's initial speed and the direction and magnitude of its acceleration allow us to infer that the initial velocity is crucial to determine the subsequent motion of the block as it slows down, stops, and moves in the opposite direction with increasing speed.
In conclusion, the initial velocity of the block as described in the problem is 12.0 m/s east, which is the starting speed of the block before any acceleration has been applied.