1. There's an spheric bubble in the air with a radius of 3.2 cm. You blow air inside the bubble until its radius gets 5.8 cm. Which is the work done on the bubble? Consider the (constant) superficial tension of the bubble as 26 N/m. 2. The heart pumps 75 ml of blood in each beating with an average pressure of 110 mmHg. It beats 65 times per minute. Calculate the power of pumping of the heart.