1)A stone of mass 20g is released from a catapult whose rubber has been stretching through 4cm. if the force constant of the rubber is 200Nm^-1, calculate the velocity with which the stone leaves the catapult 2)A spiral spring is compressed by 0.02m. calculate the energy stored in the spring, if the force constant is 400Nm^-1​

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?