Final answer:
The extra force exerted against the bottom of the jug is equal to the force exerted by the cork, which is 120 N.
Step-by-step explanation:
The extra force exerted against the bottom of the jug can be calculated using the concept of pressure. Pressure is defined as force divided by area. In this case, since the bottom of the jug broke away, we can assume that the force exerted by the cork is equal to the force exerted against the bottom of the jug. Therefore, the extra force exerted against the bottom is equal to the force exerted by the cork, which is 120 N.