A 2.0-kg block sliding on a horizontal frictionless surface is attached to one end of a horizontal spring (k = 200 N/m) which has its other end fixed. If the block has a speed of 4.0 m/s as it passes through the equilibrium position, what is its speed when it is 20 cm from the equilibrium position?
1) 2.6 m/s
2) 3.1 m/s
3) 3.5 m/s
4) 1.9 m/s
5) 2.3 m/s
Answer: 3