A 0.50kg mass is attached to a spring with constant 200Nm−1 and oscillates horizontally with amplitude 0.10m. What is the speed of the mass when the elastic potential energy is 25% of the total mechanical energy?
(a) 0.87ms−1
(b) 2.45ms−1
(c) 1.73ms−1
(d) 1.41ms−1