Ga (hypothetical) large slingshot is stretched 1.5 m to launch a 160 g projectile with speed sufficient to escape from earth (11.2 km/s). assume the elastic bands of the slingshot obey hooke's law. (a) what is the spring constant of the device, if all the elastic potential energy is converted to kinetic energy? (b) assume that an average person can exert a force of 440 n. how many people are required to stretch the elastic bands?