Posted by Vladimir on .
A 0.51kg mass is attached to a horizontal spring with k = 108 N/m. The mass slides across a frictionless surface. The spring is stretched 26 cm from equilibrium, and then the mass is released from rest.
(a) Find the mechanical energy of the system.
(b) Find the speed of the mass when it has moved 9 cm.
(c) Find the maximum speed of the mass.

Physics 
Delbarre,
this case the energy of sistem is
conservation of energy:
(1/2)kx² = (1/2)mv² then you can find the energy of springs, this energy would be the energy of total sistem because no exist friccion.
the maximum velocity of the mass v= square root((kx²)/ m)
the speed when it has moved 9 cm
x=(26 9) =17cm this x replaces in this formula.
enjoy the answer