So what we can do is apply the Hooke's law wich states that F = -kx ( P.S the -ve sign means opposite in direction ) Also we will need to determine the spring's constant with the formula: k = F / x Where F = the force ( = 20 N ) x = the displacement of the end of the spring from it's position ( = 0.20 m ) k = the spring's constant ( = unknown ) So this would be: k = 20 / 0.20 = 100 N/m The period of oscillation of 4 kg : T = 2 * pi * square root m / k T = 2 * pi * square root 4 / 100 T = 1.256 seconds Hope it helps
