A disk of mass 10 gm is kept horizontaly in air by firing bullets of mass 5 g each. each at the rate of 10/s. If the bullet rebounds with which the bullets are fired is

Question

\[(a)\;49\; cm/s \quad (b)\;98\; cm/s \quad (c)\;147\; cm/s \quad(d)\;196\; cm/s \]