Final answer:
The block's acceleration on a frictionless surface, given its weight of 120 N and a spring force of 60 N, is approximately 4.9 m/s², therefore the closest answer is 4 m/s² (option a).
Step-by-step explanation:
The question asks about the acceleration of a block attached to a spring on a frictionless surface. Given that the block weighs 120 N and the scale reads 60 N, we can determine the acceleration using Newton's second law of motion. The block's weight acts downward while the scale reading suggests a lesser force, indicating that the spring is pulling upwards with a force of 60 N.
Since weight is the product of mass and gravity (W = mg), we can find the mass (m) by dividing the weight by the acceleration due to gravity (g = 9.8 m/s²). Thus, m = 120 N / 9.8 m/s² = 12.24 kg. According to Newton's second law, F = ma, where F is the net force (60 N in this case), m is the mass, and a is the acceleration. We solve for acceleration (a) by rearranging the formula to a = F/m = 60 N / 12.24 kg.
By calculating, the acceleration of the block is approximately 4.90 m/s². Therefore, the correct answer to the provided question would be (a) 4 m/s², as it is the closest value to our calculated acceleration of 4.90 m/s².