Question

A 1.0 kg mass attached to a spring is pulled back horizontally across a table so that the potential energy of the system is increased from zero to 190 J. Ignoring friction, what is the kinetic energy of the system after the mass is released and has moved to a point where the potential energy has decreased to 50 J?

Answer 1

Initial Potential Energy for spring:\[PE_{i}=190J\]Final Potential Energy for spring:\[PE_{f}=50J\]For no friction energy is conserved --> the difference must have been converted to kinetic energy:\[KE=PE_{f}-PE_{i}=140J\]