1. A body of mass m is attached to the lower end of a spring whose upperend is fixed. The spring has negligible mass. When the mass m is slightly pulled down and released, it oscillates with a time period of \(3\, s\). When the mass m is increased by \(1\, kg\), the time period of oscillationsbecomes \(5\, s\). The value of \(m\) in kg is